📚 Update documentation for byterator

Problem:
- `byterator` doesn't document the 64-bit functionality.
- Documentation for supported compilers is out of date.

Solution:
- Update `byterator` docs to add 64-bit functions.
- Update documentation for supported toolchains.

Author: elbeno

README.md

@@ -11,7 +11,7 @@ Some of the extras are available only with C++20 or later.
 
 *stdx* supports:
 
-- clang 14 through 19
+- clang 14 through 20
 - gcc 12 through 14
 
 See the [full documentation](https://intel.github.io/cpp-std-extensions/).

docs/byterator.adoc

@@ -72,6 +72,10 @@ i.writeu16(v16);        // write and advance
 auto v32 = i.peeku32(); // read value without advancing
 v32 = i.readu32();      // read and advance
 i.writeu32(v32);        // write and advance
+
+auto v64 = i.peeku64(); // read value without advancing
+v64 = i.readu64();      // read and advance
+i.writeu64(v64);        // write and advance
 ----
 
 These convenience functions are implemented by function templates that offer

docs/intro.adoc

@@ -21,8 +21,11 @@ The following compilers are supported:
 * clang 16
 * clang 17
 * clang 18
+* clang 19
+* clang 20
 * gcc 12
 * gcc 13
+* gcc 14
 
 In general, `stdx` supports the C++17 standard; however some functionality is
 available only in 20 and later.