Add env variable support for number of followable hashtags in feed column (#2500)

* Add env variable support for number of followable hashtags in feed column.

* Add a note about performance concerns for higher values.

See discussion in https://github.com/glitch-soc/mastodon/pull/2500

* Update .devcontainer/docker-compose.yml

---------

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/features/hashtag_timeline/components/column_settings.jsx

@@ -9,6 +9,8 @@ import { NonceProvider } from 'react-select';
 import AsyncSelect from 'react-select/async';
 import Toggle from 'react-toggle';
 
+import { maxFeedHashtags } from 'flavours/glitch/initial_state';
+
 import SettingToggle from '../../notifications/components/setting_toggle';
 
 const messages = defineMessages({
@@ -46,9 +48,9 @@ class ColumnSettings extends PureComponent {
   onSelect = mode => value => {
     const oldValue = this.tags(mode);
 
-    // Prevent changes that add more than 4 tags, but allow removing
-    // tags that were already added before
-    if ((value.length > 4) && !(value < oldValue)) {
+    // Prevent changes that add more than the number of configured
+    // tags, but allow removing tags that were already added before
+    if ((value.length > maxFeedHashtags) && !(value < oldValue)) {
       return;
     }
 

app/javascript/flavours/glitch/initial_state.js

@@ -67,6 +67,7 @@ export const hasMultiColumnPath = initialPath === '/'
  * @property {InitialStateMeta} meta
  * @property {object} local_settings
  * @property {number} max_toot_chars
+ * @property {number} max_feed_hashtags
  * @property {number} poll_limits
  */
 
@@ -130,6 +131,7 @@ export const sso_redirect = getMeta('sso_redirect');
 
 // Glitch-soc-specific settings
 export const maxChars = (initialState && initialState.max_toot_chars) || 500;
+export const maxFeedHashtags = (initialState && initialState.max_feed_hashtags) || 4;
 export const favouriteModal = getMeta('favourite_modal');
 export const pollLimits = (initialState && initialState.poll_limits);
 export const defaultContentType = getMeta('default_content_type');