refactor: convert js to ts

[SuaYoo]

Fixes the following build error on import in Angular projects:

ERROR in node_modules/@telnyx/webrtc/lib/BaseClient.d.ts:1:26 - error TS2307: Cannot find module './TypedEmitter'.

1 import TypedEmitter from './TypedEmitter';
                           ~~~~~~~~~~~~~~~~
node_modules/@telnyx/webrtc/lib/Verto/Verto.d.ts:1:28 - error TS2307: Cannot find module './LiveArray'.

1 import VertoLiveArray from './LiveArray';
                             ~~~~~~~~~~~~~
node_modules/@telnyx/webrtc/lib/Verto/Verto.d.ts:2:23 - error TS2307: Cannot find module './ConfMan'.

2 import VertoConf from './ConfMan';
                        ~~~~~~~~~~~
node_modules/@telnyx/webrtc/lib/Verto/Verto.d.ts:3:25 - error TS2307: Cannot find module './Dialog'.

3 import VertoDialog from './Dialog';

See microsoft/TypeScript#7546 (comment)

Manual testing

1. Run npm link
2. Outside of this repo, generate new project with Angular CLI and install @telnyx/webrtc
3. From the Angular project, run npm link @telnyx/webrtc
4. Import TelnyxRTC and start app with ng serve. App should compile without errors

Warning I haven't tested actual calls as of 4d59d0f

[DeividVeloso]

Nice!