gh-119786: Move parser doc from devguide to InternalDocs (#125119)

Co-authored-by: Jacob Coffee <[email protected]>
Co-authored-by: Carol Willing <[email protected]>
Co-Authored-By: Adam Turner <[email protected]>
Co-Authored-By: Carl Friedrich Bolz-Tereick <[email protected]>
Co-Authored-By: Carol Willing <[email protected]>
Co-Authored-By: Erlend E. Aasland <[email protected]>
Co-Authored-By: Ezio Melotti <[email protected]>
Co-Authored-By: Hugo van Kemenade <[email protected]>
Co-Authored-By: Irit Katriel <[email protected]>
Co-Authored-By: Itamar Ostricher <[email protected]>
Co-Authored-By: Julien Palard <[email protected]>
Co-Authored-By: Mana <[email protected]>
Co-Authored-By: Muhammad Mahad <[email protected]>
Co-Authored-By: Ned Batchelder <[email protected]>
Co-Authored-By: Pablo Galindo Salgado <[email protected]>
Co-Authored-By: slateny <[email protected]>
Co-Authored-By: wookie184 <[email protected]>

Author: 16 people

InternalDocs/README.md

@@ -12,6 +12,8 @@ it is not, please report that through the
 [issue tracker](https://github.com/python/cpython/issues).
 
 
+[Guide to the parser](parser.md)
+
 [Compiler Design](compiler.md)
 
 [Frames](frames.md)