Rewrite extension, call API manually, take advantage of features not supported by the current library (#24)

This PR updates the entire extension. It will not use a library that has not been updated for years, so it should work with newer versions of PHP.
Additionally, it sends more information to the Akismet API to make spam detection more accurate.
The Akismet class can be used by other extensions.

Todo:
- [x] Convert frontend to TypeScript
- [x] Call Akismet API manually
- [x] Option to remove blatant spam
- [x] Permission to bypass Akismet
- [x] Sending additional parameters like `is_test`

Nice to have, but can be left for another PR:
- [ ] Suspend obvious spamers
- [ ] Send  `blog_lang` parameter
- [ ] Checking post edits

Sponsored by [forum.android.com.pl](https://forum.android.com.pl/)

extensions/akismet/locale/en.yml

@@ -7,10 +7,14 @@ flarum-akismet:
   # Translations in this namespace are used by the admin interface.
   admin:
 
-    # These translations are used in the Akismet Settings modal dialog.
+    # These translations are used in the Akismet Settings.
     akismet_settings:
       api_key_label: API Key
       title: Akismet Settings
+      delete_blatant_spam_label: Automatically delete blatant spam
+      delete_blatant_spam_help: If Akismet has determined that the comment is blatant spam, instead of flagging, automatically delete post
+    permissions:
+      bypass_akismet: Bypass Akismet
 
   # Translations in this namespace are used by the forum user interface.
   forum: