Updated package.json to export type definitions

[RaffaeleSgarro]

Without the types key in the export section of package.json the typescript compiler complains that cannot find a declaration file:

error TS7016: Could not find a declaration file for module '@vueuse/sound'. 'C:/[redacted]/node_modules/@vueuse/sound/dist/index.mjs' implicitly has an 'any' type.
  There are types at 'C:/[redacted]/node_modules/@vueuse/sound/dist/index.d.ts', but this result could not be resolved when respecting package.json "exports". The '@vueuse/sound' library may need to update its package.json or typings.

21 import { useSound } from '@vueuse/sound';
                            ~~~~~~~~~~~~~~~


Found 1 error in src/App.vue:21

ERROR: "type-check" exited with 2.

Closes #42

[oliver139]

I think this is quite a urgent issue with simple solution. Hope this PR can be merge so soon..

[mshamaseen]

The package doesn't work on new TS versions, hope this PR resolve it soon

[mshamaseen]

would appreciate if you can merge this @Tahul

[Sengulair]

Hope this will be merged soon. Import problem with types error still exist

[Emily-0616]

I sincerely hope to get your help @Tahul

[makroxyz]

Please merge!

[ezBeanie]

Can this be merged?

[oliver139]

@Tahul Is this repo no longer maintain?

[itsrafsanjani]

@Tahul Can you please merge this?