build: stops ignoring .env files from docker context so env variables get set during react app build. (#5809)

build: stops ignoring .env.development and .env.production files from docker context so env variables get set during react app build.
* this fixes the issue where Browse Libraries button link was broken in
  docker/self-hosted versions of excalidraw

.dockerignore

@@ -1,5 +1,6 @@
 *
-!.env
+!.env.development
+!.env.production
 !.eslintrc.json
 !.npmrc
 !.prettierrc