Add new interfaces to the docs

Author: mborland

doc/decimal/charconv.adoc

@@ -88,6 +88,18 @@ namespace decimal {
 template <typename DecimalType>
 constexpr boost::decimal::from_chars_result from_chars(const char* first, const char* last, DecimalType& value, boost::decimal::chars_format fmt = boost::decimal::chars_format::general) noexcept
 
+#ifdef BOOST_DECIMAL_HAS_STD_STRING_VIEW
+
+template <typename DecimalType>
+constexpr boost::decimal::from_chars_result from_chars(std::string_view str, DecimalType& value, boost::decimal::chars_format fmt = boost::decimal::chars_format::general) noexcept
+
+#else
+
+template <typename DecimalType>
+constexpr boost::decimal::from_chars_result from_chars(const std::string& str, DecimalType& value, boost::decimal::chars_format fmt = boost::decimal::chars_format::general) noexcept
+
+#endif
+
 #ifdef BOOST_DECIMAL_HAS_STD_CHARCONV
 
 template <typename DecimalType>

doc/decimal/config.adoc

@@ -46,3 +46,5 @@ This flag increases the performance of the basis operations (e.g. add, sub, mul,
 - `BOOST_DECIMAL_HAS_STD_CHARCONV`: This macro is defined if header `<charconv>` exists and the language standard used is >= C++17
   * We only need the structs and enums out of the header so we are not concerned with being overly restrictive about the feature test macros.
     ** Known compilers that support this lighter  requirement are: GCC >= 10, Clang >= 13, and MSVC >= 14.2
+
+- `BOOST_DECIMAL_HAS_STD_STRING_VIEW`: This macro is defined if header `<string_view>` exists and the langauge standard used is >= C++17