📝 add more API documentation

doc/mkdocs/docs/api/basic_json/accept.md

@@ -0,0 +1,88 @@
+# basic_json::accept
+
+```cpp
+// (1)
+template<typename InputType>
+static bool accept(InputType&& i,
+                   const bool ignore_comments = false);
+
+// (2)
+static bool accept(iterator first, iterator last,
+                   const bool ignore_comments = false);
+static bool accept(const_iterator first, const_iterator last,
+                   const bool ignore_comments = false);
+```
+
+Checks whether the input is valid JSON.
+
+1. Reads from a compatible input.
+2. Reads from a pair of character iterators
+    
+    The value_type of the iterator must be a integral type with size of 1, 2 or 4 bytes, which will be interpreted
+    respectively as UTF-8, UTF-16 and UTF-32.
+    
+Unlike the [`parse`](parse.md) function, this function neither throws an exception in case of invalid JSON input
+(i.e., a parse error) nor creates diagnostic information.
+
+## Template parameters
+
+`InputType`
+:   A compatible input, for instance:
+    
+    - an `std::istream` object
+    - a `FILE` pointer
+    - a C-style array of characters
+    - a pointer to a null-terminated string of single byte characters
+    - an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.
+
+## Parameters
+
+`i` (in)
+:   Input to parse from.
+
+`ignore_comments` (in)
+:   whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
+    (`#!cpp false`); (optional, `#!cpp false` by default)
+
+`first` (in)
+:   iterator to start of character range
+
+`last` (in)
+:   iterator to end of character range
+
+## Return value
+
+Whether the input is valid JSON.
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+## Complexity
+
+Linear in the length of the input. The parser is a predictive LL(1) parser.
+
+## Notes
+
+(1) A UTF-8 byte order mark is silently ignored.
+
+## Examples
+
+??? example
+
+    The example below demonstrates the `accept()` function reading from a string.
+
+    ```cpp
+    --8<-- "examples/accept__string.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/accept__string.output"
+    ```
+
+## Version history
+
+- Added in version 3.0.0.
+- Ignoring comments via `ignore_comments` added in version 3.9.0.