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/vauth/digest.c

@@ -216,7 +216,7 @@ static bool auth_digest_get_key_value(const char *chlg, const char *key,
       if(curlx_str_cmp(&name, key)) {
         /* if this is our key, return the value */
         if(curlx_strlen(&data) >= buflen)
-          /* doesn't fit */
+          /* does not fit */
           return FALSE;
         memcpy(buf, curlx_str(&data), curlx_strlen(&data));
         buf[curlx_strlen(&data)] = 0;