#43 added typescript support

[Felix-Franz]

According to #43 I have created an index.d.ts and included it in the package.json, but I am not 100% sure if this works if the package is published to the npm registry.
The easiest way to check this is to test it after it is published to the npm.

[this-fifo]

thanks @Felix-Franz , ideally we would want to avoid having any types, but that would require maintaining the values supported by Jitsi. This is a good start as it already adds value 🙇‍♂️