Add source for character mappings (GH-92014) (#92388)

(cherry picked from commit d707d07)

Co-authored-by: slateny <46876382+slateny@users.noreply.github.com>

Co-authored-by: slateny <46876382+slateny@users.noreply.github.com>

Author: miss-islington

Lib/html/entities.py

@@ -4,6 +4,7 @@
 
 
 # maps the HTML entity name to the Unicode code point
+# from https://html.spec.whatwg.org/multipage/named-characters.html
 name2codepoint = {
     'AElig':    0x00c6, # latin capital letter AE = latin capital ligature AE, U+00C6 ISOlat1
     'Aacute':   0x00c1, # latin capital letter A with acute, U+00C1 ISOlat1