feature: support add-exclude

[dekelund]

• [x] Ready for review
• [x] Follows CONTRIBUTING rules
• [x] Reviewed by Snyk internal team

What it does

Add function to provide file paths to be added to exclude-section in policy-files.

• Add function addExclude, to add file path-patterns to a policy object.
• Add validation of the exclude-group:
  • global -- for files to ignore by unmanaged, and Snyk Code
  • code -- for files being ignored by Snyk Code
• Add logic to prevent duplication of patterns within the same group.

How should this be manually tested?

In an upcoming release of the CLI, it will be used by following command:

snyk ignore --file-path='./vendor/*.ts' --file-path-group='global'

[CLAassistant]

All committers have signed the CLA.

[snyksec]

:tada: This PR is included in version 1.23.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: