[ENG-83] Update README.md

[syncom]

Add example usage. Fix typos.

[linear]

ENG-83 Create a GitHub action to allow OTA release to be made from GitHub workflows

Create a GitHub action to allow an OTA release to be done from a build pipeline. Sample syntax to use the GitHub action in a GHA workflow

- name: 'OTA release'
  uses: thistletech/ota-releasev1.0.0
  with:
    releaseType: 'file' (or 'archive' or 'rootfs')
    artifact: /path/to/artifacts
    fileBasePathOnTarget: /path/to/target-base-dir 
    projectAccessToken: ${{ secrets.THISTLE_TOKEN }}
    signingKeyManagement: 'remote' (or 'local')