Add types to package exports

[MI3Guy]

Motivation

When using TypeScript with "module": "ES2022" with a package that defines exports, the exports mapping takes priority over types. This means that the type definitions are looked up based on the .js (or .mjs) files under dist, causing them to not be found.

Expected behavior

TypeScript finds the type definitions.

Actual behavior

TypeScript complains about missing type definitions.

This can be fixed by adding

"types": "./astring.d.ts",

as the first entry under exports.

[Tom Golden]

Added context:

[David Bonnet]

Thanks @MI3Guy for reporting this. It is fixed in 36c0029.