feat: Update TS & react-docgen-typescript and support parser config

[michaeltaranto]

Update react-docgen-typescript and add support for customising the parser config by specifying reactDocgenTypescriptConfig in your playroom.config.js.

module.exports = {
  ...,
  reactDocgenTypescriptConfig: {
    propFilter: (prop, component) => {
      ...
    }
  }
};

Full change list:

• Update react-docgen-typescript to ^2.1.0 (Closes https://github.com/seek-oss/playroom/issues/230)
• Update typescript to ^4.3.2 (Closes https://github.com/seek-oss/playroom/issues/230)
• Support customising the docgen parser config (Closes https://github.com/seek-oss/playroom/pull/130)
• Default parser config now supports TS enums and literal unions (Closes https://github.com/seek-oss/playroom/issues/128)
• Default prop filtering no longer omits className, only children. Although you can now customise the the propFilter as per example above (Closes https://github.com/seek-oss/playroom/issues/91, https://github.com/seek-oss/playroom/issues/194, )
• Enable noErrorTruncation on top of users tsconfig to ensure prop values are not truncated (as pointed out by @jesstelford in https://github.com/seek-oss/playroom/pull/220)
• Removed internal examples folder due to rot and maintenance overhead