[tools] Add docs to setup (#197)

Author: oliviertassinari

tools-public/README.md

@@ -1 +1,20 @@
-# tools-private.mui.com
+# tools-public.mui.com
+
+## .env
+
+This application relies on the following environment variables.
+You need to create a `.env` file in the same folder as this README file and fill in the values.
+
+```shell
+GITHUB_MUI_BOT2_PUBLIC_REPO_TOKEN=
+GITHUB_TOKEN= # https://github.com/settings/tokens with no scopes
+GOOGLE_SHEET_TOKEN=
+HIBOB_TOKEN_READ_STANDARD=
+STORE_PRODUCTION_READ_DATABASE=
+STORE_PRODUCTION_READ_HOST=
+STORE_PRODUCTION_READ_PASSWORD=
+STORE_PRODUCTION_READ_USERNAME=
+ZENDESK=
+```
+
+Those values are actually a subset of https://github.com/mui/mui-private/blob/master/tools-private/README.md#env.