Move .editorconfig to repo root (#24398)

* Move .editorconfig to repo root

* Add yaml formatting to .editorconfig

webapp/channels/.editorconfig

@@ -1,32 +0,0 @@
-# http://editorconfig.org/
-
-root = true
-
-[*]
-end_of_line = lf
-insert_final_newline = true
-trim_trailing_whitespace = true
-charset = utf-8
-
-[*.go]
-indent_style = tab
-
-[*.{js,jsx,json,html,ts,tsx}]
-indent_style = space
-indent_size = 4
-
-[{package.json,.eslintrc.json}]
-indent_size = 2
-
-[i18n/**.json]
-indent_size = 2
-
-[Makefile]
-indent_style = tab
-
-[*.scss]
-indent_style = space
-indent_size = 4
-
-[.npm-upgrade.json]
-insert_final_newline = false