fix: Improve composer.lock behavior with ignore-cache

[flagbrad]

Description

Fixes a bug where composer.lock is not honored if ignore-cache is set to true. Also, the recently added require-lock-file option had not been incorporated into tests and documentation, so added a test and docs (and fixed small typo in CONTRIBUTING)

Motivation and context

Fixes #259. Discovered by our team when we decided to ignore cache and then noticed deployment's composer packages did not match our local dev packages.

How has this been tested?

Unfortunately, I know of no way to test action.yml without actually merging it and then trying it as a GitHub action.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

PR checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes.

[flagbrad]

@ramsey I think I fixed the problem that caused this test run to fail. I was seeing this locally, but assumed it was a problem with my version of expect or something. All tests are passing locally now.