[libc++] Add link to the Github conformance table from the documentation

Author: ldionne

libcxx/docs/Status/Cxx17.rst

@@ -18,8 +18,6 @@ In February 2017, the C++ standard committee approved this draft, and sent it to
 
 This page shows the status of libc++; the status of clang's support of the language features is `here <https://clang.llvm.org/cxx_status.html#cxx17>`__.
 
-.. attention:: Features in unreleased drafts of the standard are subject to change.
-
 The groups that have contributed papers:
 
 -  CWG - Core Language Working group

libcxx/docs/Status/Cxx20.rst

@@ -18,8 +18,6 @@ In September 2020, the C++ standard committee approved this draft, and sent it t
 
 This page shows the status of libc++; the status of clang's support of the language features is `here <https://clang.llvm.org/cxx_status.html#cxx20>`__.
 
-.. attention:: Features in unreleased drafts of the standard are subject to change.
-
 The groups that have contributed papers:
 
 -  CWG - Core Language Working group

libcxx/docs/Status/Cxx23.rst

@@ -18,8 +18,6 @@ In February 2023, the C++ standard committee approved this draft, and sent it to
 
 This page shows the status of libc++; the status of clang's support of the language features is `here <https://clang.llvm.org/cxx_status.html#cxx23>`__.
 
-.. attention:: Features in unreleased drafts of the standard are subject to change.
-
 The groups that have contributed papers:
 
 -  CWG - Core Language Working group

libcxx/docs/index.rst

@@ -168,8 +168,13 @@ to be formally supported and listed here, please work with the libc++ team to se
 up testing for your configuration.
 
 
-C++ Dialect Support
-===================
+C++ Standards Conformance
+=========================
+
+Libc++ provides full support for C++11 and C++14, and provides most of newer standards
+with a few omissions. The conformance status of the library's tip is tracked in real-time
+using `this page <https://github.com/orgs/llvm/projects/31>`_. The conformance status of
+this release is described in the pages below:
 
 * C++11 - Complete
 * C++14 - Complete