DevX: Add another Matrix site to docker-compose (#3511)

* remove redis, since we dont use it

* update localhost TLS certificat to add *.othersite.m.localhost wildcard

* allow for federation

* Add services and config files for Matrix site othersite.m.localhost

* add element web instance app.othersite.m.localhost

* update README

* exclude synapse database for othersite.m.localhost

* linting

.gitignore

@@ -8,6 +8,7 @@ dist-ssr
 .idea/
 public/config.json
 backend/synapse_tmp/*
+backend/synapse_tmp_othersite/*
 /coverage
 config.json
 
@@ -28,4 +29,4 @@ yarn-error.log
 /test-results/
 /playwright-report/
 /blob-report/
-/playwright/.cache/
+/playwright/.cache/