[skip ci] basic sync envs docs workflow

.github/workflows/sync-envs-docs.yaml

+name: Sync ENV variables docs
+
+on:
+    workflow_dispatch:
+
+jobs:
+    run:
+        name: Run
+        runs-on: ubuntu-latest
+        steps:
+            -   name: Copy files to Blockscout Docs repository
+                uses: lubu12/copy-files-to-repository@v1
+                env:
+                    API_TOKEN_GITHUB: ${{ secrets.GITHUB_TOKEN }}
+                with:
+                    source-files: 'docs/ENVS.md docs/DEPRECATED_ENVS.md'
+                    destination-username: 'blockscout-bot'
+                    destination-repository: 'blockscout/docs'
+                    destination-directory: 'docs/setup/env-variables/frontend-common-envs'
+                    commit-email: 'tom@blockscout.com'