badwords: check indented lines in source code, fix fallouts

- badwords.pl: add `-a` option to check all lines in source code files.
  Before this patch indented lines were skipped (to avoid Markdown code
  fences.)
- GHA/checksrc: use `-a` when verifying the source code.
- GHA/checksrc: disable `So` and `But` rules for source code.
- GHA/checksrc: add docs/examples to the verified sources.
- badwords.txt: delete 4 duplicates.
- badwords.txt: group and sort contractions.
- badwords.txt: allow ` url = `, `DIR`, `<file name`.

Closes #19536

lib/urlapi.c

@@ -1940,7 +1940,7 @@ nomem:
         if(!n)
           bad = TRUE; /* empty hostname is not okay */
         else if(!urlencode) {
-          /* if the host name part was not URL encoded here, it was set ready
+          /* if the hostname part was not URL encoded here, it was set ready
              URL encoded so we need to decode it to check */
           size_t dlen;
           char *decoded = NULL;