feat: add alias support

[aarlaud]

• Tests written and linted
• Documentation written / README.md updated https://snyk.io/docs/snyk-for-node/
• Follows CONTRIBUTING agreement
• Commit history is tidy https://git-scm.com/book/en/v2/Git-Branching-Rebasing
• Reviewed by Snyk team

What this does

Introduces support for npm and yarn aliases to alternative packages using npm aliases.
It reflects the true dependencies being aliased to in the depgraph, which means the referenced package(s), the one(s) usually imported, will not appear in the depgraph which will show the aliased package instead.

Notes for the reviewer

• The alias support is aimed to be an opt-in only capability that operators will need to explicitly add as CLI argument. The relevant CLI change will be provided if this approach is validated.
• Prod aliases usage is generally discouraged
• aliases are generally only usable at the top level only. While workarounds might exist to use aliased packages for transitive dependencies, the aliased transitive deps use case is not covered here.

[CLAassistant]

All committers have signed the CLA.

[MarcusArdelean]

Reviewed the code and it looks good from a functionality/design point of view.

Can I ask where did the request for this feature came from? We will need to discuss this further with the team before merging it. Maybe there are other releases planned that will impact this in some sort of way that I'm not aware of.

[snyksec]

🎉 This PR is included in version 2.2.0 🎉

The release is available on:

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

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