Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/.editorconfig

@@ -0,0 +1,27 @@
+# http://editorconfig.org/
+
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+
+[*.{go,sql}]
+indent_style = tab
+
+[*.{js,jsx,json,html}]
+indent_style = space
+indent_size = 4
+
+[i18n/**.json]
+indent_size = 2
+
+[Makefile,*.mk]
+indent_style = tab
+
+[*.md]
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = false