bug: typescript should be a dev dependency

[roerohan]

https://github.com/roerohan/react-vnc/blob/574b631a53402ea3c36b1745d4b725b2c3f6d9c9/package.json#L35

Since typescript is a dependency, any project using a different version of typescript will fail to run npm install react-vnc and throw an error like the following:

npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR! 
npm ERR! Found: typescript@4.4.4
npm ERR! node_modules/typescript
npm ERR!   typescript@"^4.0.3" from the root project
npm ERR!   typescript@"^4.2.4" from react-vnc@0.2.5
npm ERR!   node_modules/react-vnc
npm ERR!     react-vnc@"0.2.5" from the root project

[roerohan]

Resolved in #20