fix: Enable reading of high priority emoji with Variant Selector 16 appended

[claremacrae]

Description

Fix parsing of Priority emoji with Variant Selector 16 appended.

Motivation and Context

Fixes #2273.

How has this been tested?

• New tests, initially failing.
• Manual exploratory testing - confirming I could reproduce the problem behaviour before the fix, and that it was then behaving correctly afterwards.

Screenshots (if appropriate)

None.

Types of changes

Changes visible to users:

• Bug fix (prefix: fix - non-breaking change which fixes an issue)

Internal changes:

• Tests (prefix: test - additions and improvements to unit tests and the smoke tests)

Checklist

• My code follows the code style of this project and passes yarn run lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change has adequate Unit Test coverage.

Terms

• My contribution follow this project's contributing guide
• I agree to follow this project's Code of Conduct