Clean up and document project files

docs/mkdocs/docs/api/basic_json/end_pos.md

@@ -6,7 +6,9 @@ constexpr std::size_t end_pos() const noexcept;
 #endif
 ```
 
-Returns the position after the last character of the JSON string the value was parsed from.
+Returns the position immediately following the last character of the JSON string from which the value was parsed,
+provided the value originated from a string. If the value was constructed by other means, the function returns
+`std::string::npos`.
 
 | JSON type | return value                      |
 |-----------|-----------------------------------|

docs/mkdocs/docs/api/basic_json/start_pos.md

@@ -6,7 +6,8 @@ constexpr std::size_t start_pos() const noexcept;
 #endif
 ```
 
-Returns the position of the first character of the JSON string the value was parsed from.
+Returns the position of the first character in the JSON string from which the value was parsed, provided the value
+originated from a string. If the value was constructed by other means, the function returns `std::string::npos`.
 
 | JSON type | return value                                   |
 |-----------|------------------------------------------------|

docs/mkdocs/docs/api/macros/json_diagnostic_positions.md

@@ -10,7 +10,8 @@ When enabled, two new member functions [`start_pos()`](../basic_json/start_pos.m
 [`end_pos()`](../basic_json/end_pos.md) are added to [`basic_json`](../basic_json/index.md) values.
 [`start_pos()`](../basic_json/start_pos.md) returns the start position of that JSON value in the original JSON string
 the object was parsed from. Likewise, [`end_pos()`](../basic_json/end_pos.md) returns the end position of that JSON
-value in the original string the object was parsed from.
+value in the original string the object was parsed from. If the value was not parsed, but constructed by other means,
+the functions returns `std::string::npos`.
 
 [`start_pos()`](../basic_json/start_pos.md) returns the first character of a given value in the original JSON string,
 while [`end_pos()`](../basic_json/end_pos.md) returns the character _following_ the last character. For objects and
@@ -31,11 +32,9 @@ Given the above, [`end_pos()`](../basic_json/end_pos.md)` - `[`start_pos()`](../
 value provides the length of the parsed JSON string for that value, including the opening or closing braces, brackets,
 or quotes.
 
-[`start_pos()`](../basic_json/start_pos.md) and [`end_pos()`](../basic_json/end_pos.md) are only set if the JSON value
-was parsed using [`parse()`](../basic_json/parse.md). For all other cases,`std::string::npos` will be returned.
-
 Note that enabling this macro increases the size of every JSON value by two `std::size_t` fields and adds slight runtime
-overhead.
+overhead to parsing, copying JSON value objects, and the generation of error messages for exceptions. It also causes
+these values to be reported in those error messages.
 
 ## Default definition