Convert typings to .d.ts files

[NotWoods]

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Shipping .ts files instead of .d.ts files for TypeScript code that never runs creates issues for some consumers. If there's a typing bug, such as EventPathParameters being unused, there's no way to turn off the error.

I also changed uses of Array to ReadonlyArray, to support returning both normal arrays and the readonly variant.

List other issues or pull requests related to this problem

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Describe the solution you've chosen

By using .d.ts files, consumers can use the skipLibCheck option and ignore type errors from them.

Describe alternatives you've considered

None

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[eduardoboucas]

Looks great, thanks!

[eduardoboucas]

This has been released as version 0.7.1.