Consolidate documentation (#3071)

* 🦚 consolidate documentation
* ♻️ overwork std specializations
* 🦃 move images files to mkdocs
* ♻️ fix URLs
* 🪝 tweak MkDocs configuration
* 🪝 add namespaces
* 📡 document deprecations
* 📡 document documentation generation
* 🦜 improve search
* 🦜 add examples
* 🚧 start adding documentation for macros
* 📡 add note for https://github.com/nlohmann/json/issues/874#issuecomment-1001699139
* 📡 overwork example handling
* 📡 fix Markdown tables

doc/mkdocs/docs/features/element_access/checked_access.md

@@ -27,7 +27,7 @@ The `#!cpp at()` member function performs checked access; that is, it returns a
     | `#!cpp j.at("hobbies").at(0)`  | `#!json "hiking"` |
     | `#!cpp j.at("hobbies").at(1)`  | `#!json "reading"` |
 
-The return value is a reference, so it can be modify the original value.
+The return value is a reference, so it can be modified by the original value.
 
 ??? example
 
@@ -69,9 +69,9 @@ When accessing an invalid index (i.e., an index greater than or equal to the arr
 
 ## Summary
 
-| scenario | non-const value | const value |
-| -------- | ------------- | ----------- |
-| access to existing object key | reference to existing value is returned | const reference to existing value is returned |
-| access to valid array index | reference to existing value is returned | const reference to existing value is returned |
+| scenario                          | non-const value                                | const value                                    |
+|-----------------------------------|------------------------------------------------|------------------------------------------------|
+| access to existing object key     | reference to existing value is returned        | const reference to existing value is returned  |
+| access to valid array index       | reference to existing value is returned        | const reference to existing value is returned  |
 | access to non-existing object key | `basic_json::out_of_range` exception is thrown | `basic_json::out_of_range` exception is thrown |
-| access to invalid array index | `basic_json::out_of_range` exception is thrown | `basic_json::out_of_range` exception is thrown |
+| access to invalid array index     | `basic_json::out_of_range` exception is thrown | `basic_json::out_of_range` exception is thrown |

doc/mkdocs/docs/features/element_access/index.md

@@ -1,4 +1,4 @@
-# Overview
+# Element Access
 
 There are many ways elements in a JSON value can be accessed:
 

doc/mkdocs/docs/features/element_access/unchecked_access.md

@@ -27,7 +27,7 @@ Elements in a JSON object and a JSON array can be accessed via `#!cpp operator[]
     | `#!cpp j["hobbies"][0]`  | `#!json "hiking"` |
     | `#!cpp j["hobbies"][1]`  | `#!json "reading"` |
 
-The return value is a reference, so it can be modify the original value. In case the passed object key is non-existing, a `#!json null` value is inserted which can be immediately be overwritten.
+The return value is a reference, so it can modify the original value. In case the passed object key is non-existing, a `#!json null` value is inserted which can be immediately be overwritten.
 
 ??? example
 
@@ -94,9 +94,9 @@ When accessing an invalid index (i.e., an index greater than or equal to the arr
 
 ## Summary
 
-| scenario | non-const value | const value |
-| -------- | ------------- | ----------- |
-| access to existing object key | reference to existing value is returned | const reference to existing value is returned |
-| access to valid array index | reference to existing value is returned | const reference to existing value is returned |
-| access to non-existing object key | reference to newly inserted `#!json null` value is returned | **undefined behavior**; assertion in debug mode |
-| access to invalid array index | reference to newly inserted `#!json null` value is returned; any index between previous maximal index and passed index are filled with `#!json null` | **undefined behavior**; assertion in debug mode |
+| scenario                          | non-const value                                                                                                                                      | const value                                     |
+|-----------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------|
+| access to existing object key     | reference to existing value is returned                                                                                                              | const reference to existing value is returned   |
+| access to valid array index       | reference to existing value is returned                                                                                                              | const reference to existing value is returned   |
+| access to non-existing object key | reference to newly inserted `#!json null` value is returned                                                                                          | **undefined behavior**; assertion in debug mode |
+| access to invalid array index     | reference to newly inserted `#!json null` value is returned; any index between previous maximal index and passed index are filled with `#!json null` | **undefined behavior**; assertion in debug mode |