Add GitHub Action declaration for installing cargo-binstall (#1269)

add action.yml and test it

.github/workflows/gh-action.yml

@@ -0,0 +1,36 @@
+name: Test GitHub Action installer
+on:
+  merge_group:
+  pull_request:
+    paths:
+      - install-from-binstall-release.ps1
+      - install-from-binstall-release.sh
+      - action.yml
+  push:
+    branches:
+      - main
+    paths:
+      - install-from-binstall-release.ps1
+      - install-from-binstall-release.sh
+      - action.yml
+
+jobs:
+  test-gha-installer:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ macos-latest, ubuntu-latest, windows-latest ]
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Install cargo-binstall
+        uses: ./ # uses action.yml from root of the repo
+
+      - name: Verify successful installation - display cargo-binstall's help
+        run: cargo binstall --help
+
+      - name: Verify successful installation - install example binary using cargo-binstall
+        run: cargo binstall -y ripgrep
+
+      - name: Verify successful installation - display help of installed binary
+        run: rg --help

README.md

@@ -107,6 +107,10 @@ Supported crates such as `cargo-binstall` itself can also be updated with `cargo
   - You can find a full description of errors including exit codes here: <https://docs.rs/binstalk/latest/binstalk/errors/enum.BinstallError.html>
 - Can I use it in CI?
   - Yes! For GitHub Actions, we recommend the excellent [taiki-e/install-action](https://github.com/marketplace/actions/install-development-tools), which has explicit support for selected tools and uses `cargo-binstall` for everything else.
+  - Additionally, we provide a minimal GitHub Action that installs `cargo-binstall`:
+    ```yml
+      - uses: cargo-bins/cargo-binstall@main
+    ``` 
 - Are debug symbols available?
   - Yes! Extra pre-built packages with a `.full` suffix are available and contain split debuginfo, documentation files, and extra binaries like the `detect-wasi` utility.
 

action.yml

@@ -0,0 +1,14 @@
+name: 'Install cargo-binstall'
+description: 'Install the latest version of cargo-binstall tool'
+
+runs:
+  using: composite
+  steps:
+    - name: Install cargo-binstall
+      if: runner.os != 'Windows'
+      shell: sh
+      run: curl -L --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/cargo-bins/cargo-binstall/main/install-from-binstall-release.sh | bash
+    - name: Install cargo-binstall
+      if: runner.os == 'Windows'
+      run: Set-ExecutionPolicy Unrestricted -Scope Process; iex (iwr "https://raw.githubusercontent.com/cargo-bins/cargo-binstall/main/install-from-binstall-release.ps1").Content
+      shell: powershell