publish ts declaration files

[merisbahti]

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

What does this PR do?

Configures tsc to build the d.ts artifacts for publishing.

Where should the reviewer start?

tsconfig.json

How should this be manually tested?

Check so that everything looks fine in ./dist after running npm run build

Any background context you want to provide?

Nope

What are the relevant tickets?

None that I know of

Screenshots

Additional questions

Any reason this line was commented out?

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[gitphill]

no reason why this shouldn't be on - thanks!

[gitphill]

can you sign the CLA @merisbahti - then I think we can merge

[gitphill]

Ah don't think our CircleCI build pipeline is setup to run PRs from forked repos - I've recreated here #123