📝 add examples for parsing from iterator pair (#3100)

doc/examples/parse__iterator_pair.cpp

+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a JSON text given an input with other values
+    std::vector<std::uint8_t> input = {'[', '1', ',', '2', ',', '3', ']', 'o', 't', 'h', 'e', 'r'};
+
+    // parse and serialize JSON
+    json j_complete = json::parse(input.begin(), input.begin() + 7);
+    std::cout << std::setw(4) << j_complete << "\n\n";
+}

doc/examples/parse__iterator_pair.link

+<a target="_blank" href="https://wandbox.org/permlink/hUJYo1HWmfTBLMGn"><b>online</b></a>
\ No newline at end of file

doc/examples/parse__iterator_pair.output

+[
+    1,
+    2,
+    3
+]
+

doc/examples/parse__pointers.cpp

+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a JSON text given as string that is not null-terminated
+    const char* ptr = "[1,2,3]another value";
+
+    // parse and serialize JSON
+    json j_complete = json::parse(ptr, ptr + 7);
+    std::cout << std::setw(4) << j_complete << "\n\n";
+}

doc/examples/parse__pointers.link

+<a target="_blank" href="https://wandbox.org/permlink/AWbpa8e1xRV3y4MM"><b>online</b></a>
\ No newline at end of file

doc/examples/parse__pointers.output

+[
+    1,
+    2,
+    3
+]
+

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

@@ -19,7 +19,7 @@ static basic_json parse(IteratorType first, IteratorType last,
 1. Deserialize from a compatible input.
 2. Deserialize 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
+    The `value_type` of the iterator must be an integral type with size of 1, 2 or 4 bytes, which will be interpreted
     respectively as UTF-8, UTF-16 and UTF-32.
 
 ## Template parameters
@@ -34,7 +34,10 @@ static basic_json parse(IteratorType first, IteratorType last,
     - an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.
 
 `IteratorType`
-:   a compatible iterator type
+:   a compatible iterator type, for instance.
+
+    - a pair of `std::string::iterator` or `std::vector<std::uint8_t>::iterator`
+    - a pair of pointers such as `ptr` and `ptr + len`
 
 ## Parameters
 
@@ -135,6 +138,34 @@ super-linear complexity.
     --8<-- "examples/parse__contiguouscontainer__parser_callback_t.output"
     ```
 
+??? example "Parsing from a non null-terminated string"
+
+    The example below demonstrates the `parse()` function reading from a string that is not null-terminated.
+
+    ```cpp
+    --8<-- "examples/parse__pointers.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/parse__pointers.output"
+    ```
+
+??? example "Parsing from an iterator pair"
+
+    The example below demonstrates the `parse()` function reading from an iterator pair.
+
+    ```cpp
+    --8<-- "examples/parse__iterator_pair.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/parse__iterator_pair.output"
+    ```
+
 ??? example "Effect of `allow_exceptions` parameter"
 
     The example below demonstrates the effect of the `allow_exceptions` parameter in the ´parse()` function.