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/api/json_sax/number_float.md

@@ -0,0 +1,23 @@
+# <small>nlohmann::json_sax::</small>number_float
+
+```cpp
+virtual bool number_float(number_float_t val, const string_t& s) = 0;
+```
+
+A floating-point number was read.
+
+## Parameters
+
+`val` (in)
+:   floating-point value
+
+`s` (in)
+:   string representation of the original input
+
+## Return value
+
+Whether parsing should proceed.
+
+## Version history
+
+- Added in version 3.2.0.