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/vtls/wolfssl.c

@@ -1725,7 +1725,7 @@ static CURLcode wssl_handshake(struct Curl_cfilter *cf,
   if(ret == WOLFSSL_SUCCESS &&
      conn_config->verifyhost &&
      !connssl->peer.sni) {
-    /* we have an IP address as host name. */
+    /* we have an IP address as hostname. */
     WOLFSSL_X509* cert = wolfSSL_get_peer_certificate(wssl->ssl);
     if(!cert) {
       failf(data, "unable to get peer certificate");