Add GitHub Action for publishing the extension CLI (#9542)

This PR adds a GitHub Action for publishing the extension CLI.

When the `extension-cli` tag is pushed, this Action will run, build the
`zed-extension` binary, and upload it to DigitalOcean for consumption.

This will allow us to consume the pre-built binary in the CI for the
extensions repo.

Release Notes:

- N/A

---------

Co-authored-by: Max <max@zed.dev>

.github/workflows/publish_extension_cli.yml

@@ -0,0 +1,41 @@
+name: Publish zed-extension CLI
+
+on:
+  push:
+    tags:
+      - extension-cli
+
+env:
+  CARGO_TERM_COLOR: always
+  CARGO_INCREMENTAL: 0
+
+jobs:
+  publish:
+    name: Publish zed-extension CLI
+    runs-on:
+      - ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+        with:
+          clean: false
+          submodules: "recursive"
+
+      - name: Cache dependencies
+        uses: swatinem/rust-cache@v2
+        with:
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+
+      - name: Configure linux
+        shell: bash -euxo pipefail {0}
+        run: script/linux
+
+      - name: Build extension CLI
+        run: cargo build --release --package extension_cli
+
+      - name: Upload binary
+        if: ${{ github.ref == 'refs/heads/main' }}
+        env:
+          DIGITALOCEAN_SPACES_ACCESS_KEY: ${{ secrets.DIGITALOCEAN_SPACES_ACCESS_KEY }}
+          DIGITALOCEAN_SPACES_SECRET_KEY: ${{ secrets.DIGITALOCEAN_SPACES_SECRET_KEY }}
+        run: script/upload-extension-cli ${{ github.sha }}