More documentation updates for 3.11.0 (#3553)

* mkdocs: add string_view examples

* mkdocs: reference underlying operators

* mkdocs: add operator<=> examples

* mkdocs: fix style check issues

* mkdocs: tweak BJData page

* mkdocs: add CMake option hints to macros

* mkdocs: fix JSON_DISABLE_ENUM_SERIALIZATION definition

* mkdocs: fix link to unit-udt.cpp

* mkdocs: fix "Arbitrary Type Conversions" title

* mkdocs: link to api/macros/*.md instead of features/macros.md

* mkdocs: document JSON_DisableEnumSerialization CMake option

* mkdocs: encode required C++ standard in example files

* docset: detect gsed/sed

* docset: update index

* docset: fix CSS patching

* docset: add list_missing_pages make target

* docset: add list_removed_paths make target

* docset: replace page titles with name from index

* docset: add install target for Zeal docset browser

* Use GCC_TOOL in ci_test_documentation target

docs/mkdocs/docs/api/basic_json/at.md

@@ -137,11 +137,11 @@ Strong exception safety: if an exception occurs, the original value stays intact
     --8<-- "examples/at__object_t_key_type.output"
     ```
 
-??? example "Example (2) access specified object element with bounds checking"
+??? example "Example: (2) access specified object element with bounds checking"
 
     The example below shows how object elements can be read using `at()`. It also demonstrates the different exceptions
     that can be thrown.
-        
+    
     ```cpp
     --8<-- "examples/at__object_t_key_type_const.cpp"
     ```
@@ -152,34 +152,64 @@ Strong exception safety: if an exception occurs, the original value stays intact
     --8<-- "examples/at__object_t_key_type_const.output"
     ```
 
-??? example "Example (4) access specified element via JSON Pointer"
+??? example "Example: (3) access specified object element using string_view with bounds checking"
+
+    The example below shows how object elements can be read and written using `at()`. It also demonstrates the different
+    exceptions that can be thrown.
+    
+    ```cpp
+    --8<-- "examples/at__keytype.c++17.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/at__keytype.c++17.output"
+    ```
+
+??? example "Example: (3) access specified object element using string_view with bounds checking"
+
+    The example below shows how object elements can be read using `at()`. It also demonstrates the different exceptions
+    that can be thrown.
+    
+    ```cpp
+    --8<-- "examples/at__keytype_const.c++17.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/at__keytype_const.c++17.output"
+    ```
+
+??? example "Example: (4) access specified element via JSON Pointer"
 
     The example below shows how object elements can be read and written using `at()`. It also demonstrates the different
     exceptions that can be thrown.
         
     ```cpp
-    --8<-- "examples/at_json_pointer.cpp"
+    --8<-- "examples/at__json_pointer.cpp"
     ```
     
     Output:
     
     ```json
-    --8<-- "examples/at_json_pointer.output"
+    --8<-- "examples/at__json_pointer.output"
     ```
 
-??? example "Example (4) access specified element via JSON Pointer"
+??? example "Example: (4) access specified element via JSON Pointer"
 
     The example below shows how object elements can be read using `at()`. It also demonstrates the different exceptions
     that can be thrown.
         
     ```cpp
-    --8<-- "examples/at_json_pointer_const.cpp"
+    --8<-- "examples/at__json_pointer_const.cpp"
     ```
     
     Output:
     
     ```json
-    --8<-- "examples/at_json_pointer_const.output"
+    --8<-- "examples/at__json_pointer_const.output"
     ```
 
 ## See also