(FE) Add document editing with Yorkie (#38)

* Add editor header

* Add react-redux

* Add dark / light mode

* Add codemirror editor

* Temp commit

* Connect editor with yorkie

* Fix types for yorkie plugin

* Change `y` to `Yorkie`

* Move selecting color logic to editor

* Add env file

* Add `.env.development`

* Update .gitignore

* Change serializableCheck options for redux

* Add cleanUp Code to Doc, Client

* Fix cleanUp Code

* Add toolbar to editor

* Add markdown preview

* Change markdown preview padding

* Add view / edit mode

frontend/.env.development

@@ -0,0 +1,2 @@
+VITE_YORKIE_API_ADDR='https://api.yorkie.dev'
+VITE_YORKIE_API_KEY=''

frontend/.gitignore

@@ -22,3 +22,7 @@ dist-ssr
 *.njsproj
 *.sln
 *.sw?
+
+# Environment
+.env
+.env.*