Add GitHub Action for Flux Operator CLI

[stefanprodan]

This PR adds a GitHub Action for installing the Flux Operator CLI on GitHub runners for usage in workflows.
All GitHub runners are supported, including Ubuntu, Windows, and macOS.

Usage

Example workflow for printing the latest version:

name: Check the latest version

on:
  workflow_dispatch:

jobs:
  check-latest-flux-operator-version:
    runs-on: ubuntu-latest
    steps:
      - name: Setup Flux Operator CLI
        uses: controlplaneio-fluxcd/flux-operator/actions/setup@main
        with:
          version: latest
      - name: Print Flux Operator Version
        run: flux-operator version --client

Action Inputs

Name	Description	Default
version	Flux Operator version	The latest stable release
bindir	Alternative location for the CLI	$RUNNER_TOOL_CACHE

Action Outputs

Name	Description
version	The Flux Operator CLI version that was effectively installed

[matheuscscp]

LGTM! 🚀