ci: add workflow to update on pact-ffi-released events

[YOU54F]

Aim:- Provide a CI workflow, that can be triggered on release of the Pact FFI library.

Relates to pact-foundation/pact-reference#375 , specifically Trigger dependant client libraries workflows to raise PR's

This change borrows from the existing update workflow on release of the pact-ruby-standalone.

• release trigger
  • https://github.com/pact-foundation/pact-ruby-standalone/blob/3cecd6dce82922697f1ba2a3ccdabdaebdb54be9/.github/workflows/release.yml#L46-L63

Places to change (outside this repo)

1. Release point in Pact-reference project
   1. https://github.com/pact-foundation/pact-reference/blob/fc33ad23e78698ecf1fb55eedb7dc228f96def17/.github/workflows/release.yml#L74-L81
2. Example Release
   1. https://github.com/pact-foundation/pact-reference/releases/tag/libpact_ffi-v0.4.14

Points to note

Our ci workflow for verification .github/workflows/test.yml is not triggered by updates. See related issue and workarounds

Note: - the above issue is long-standing from the existing updates, at least from my quick scan of the test runs, I couldn't see triggered when the ruby core was updated, bar those triggered manually from the UI against the branch

There are a couple of workarounds that are probably feasible. first one probably preferred at the moment as we get a visual cue somewhere outside of the actions/email notifications. The triggering repo (pact-reference) won't get a notification back regarding the failing status of a build in pact-js where it was triggered by a bot or a human

• close PR and reopen from UI
• have the update workflow that is initially triggered, run the tests as part of its workflow

[coveralls]

coverage: 37.2%. remained the same
when pulling 3b310af on ci/ffi_upgrade
into 7acfdce on master.