Reverting usage of RE2 (WIP):

**Breaking changes**

The livechat v13 introduced a new library to handle regular expressions in forbidden words, to avoid
[ReDOS](https://en.wikipedia.org/wiki/ReDoS) attacks.
Unfortunately, this library was not able to install itself properly on some systems, and some admins were not able
to install the livechat plugin.

That's why we have disabled this library in v14, and introduce a new settings to enable regexp in forbidden words.
By default this settings is disabled, and your users won't be able to use regexp in their forbidden words.

The risk by enabling this feature is that a malicious user could cause a denial of service for the chat bot, by using a
special crafted regular expression in their channel options, and sending a special crafter message in one of their
rooms. If you trust your users (those who have rights to livestream), you can enable the settings. Otherwise it is not
recommanded. See the documentation for more informations.

**Minor changes and fixes**

* Channel's forbidden words: new "enable" column.
* New settings to enable regular expressions for channel forbidden words.
* "Channel advanced configuration" settings: removing the "experimental feature" label.

languages/fr.yml

@@ -611,7 +611,7 @@ prosody_firewall_disabled_warning: "Attention : mod_firewall est désactivé d
   <a href=\"/admin/plugins/show/peertube-plugin-livechat\" target=\"_blank\">paramètres
   du plugin livechat</a> , vous devez l'activer si vous voulez que cette configuration
   soit prise en compte.\n"
-prosody_firewall_file_enabled: Activé
+enabled: Activé
 prosody_firewall_name: Nom
 prosody_firewall_name_desc: "Ne peut contenir que des caractères alphanumériques,
   des traits de soulignement et des traits d'union.\nLes scripts seront chargés par