Address the clang-tidy findings of element access and iteration

Marks the default initializer of the item's index string (needed by GCC's
-Weffc++) and, in the test, an escaped literal and a comparison of find()
with end(), which is what the test is about.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/view/iterator.hpp

@@ -183,7 +183,7 @@ class view_item
 
   private:
     iterator m_it;
-    std::string m_index{};
+    std::string m_index{}; // NOLINT(readability-redundant-member-init)
 };
 
 /// the range returned by basic_json_view::items()

single_include/nlohmann/json_view.hpp

@@ -1933,7 +1933,7 @@ class view_item
 
   private:
     iterator m_it;
-    std::string m_index{};
+    std::string m_index{}; // NOLINT(readability-redundant-member-init)
 };
 
 /// the range returned by basic_json_view::items()

tests/src/unit-json_view.cpp

@@ -505,7 +505,7 @@ TEST_CASE("json_view element access and iteration")
         std::vector<std::string> keys = {"", "x"};
         for (std::size_t n = 1; n <= 40; ++n)
         {
-            keys.push_back(std::string(n, 'k'));
+            keys.emplace_back(n, 'k');
             keys.push_back(std::string(n, 'k') + "x");
             keys.push_back("x" + std::string(n, 'k'));
         }
@@ -513,7 +513,7 @@ TEST_CASE("json_view element access and iteration")
         {
             text += (i != 0 ? ",\"" : "\"") + keys[i] + "\":" + std::to_string(i);
         }
-        text += ",\"esc\\u0061ped\":\"escaped key\"}";
+        text += ",\"esc\\u0061ped\":\"escaped key\"}"; // NOLINT(modernize-raw-string-literal)
         const json_document d = json_document::parse(text);
         const json_view root = d.root();
         for (std::size_t i = 0; i < keys.size(); ++i)
@@ -583,7 +583,7 @@ TEST_CASE("json_view element access and iteration")
             }
             CHECK(v.contains("a") == j.contains("a"));
             CHECK(v.count("a") == j.count("a"));
-            CHECK((v.find("a") == v.end()) == (j.find("a") == j.end()));
+            CHECK((v.find("a") == v.end()) == (j.find("a") == j.end())); // NOLINT(readability-container-contains): find() is what is tested
         }
 
         // where basic_json has undefined behavior, the view answers safely