Remove quotes from default values / non-string values.

[strothj]

trafficstars

Will default values always be surrounded by quotes? I feel for the above delay1, the default value shoudl be 250, not "250". Is it possible to accomplish that?

Originally posted by @city41 in https://github.com/strothj/react-docgen-typescript-loader/issues/5#issuecomment-506434918

[strothj]

Currently the default values are surrounded by quotes. I'm not sure if this comes from @storybook/addon-info or if it comes from react-docgen-typescript so it will need some investigation.

[Kosai106]

I've encountered this today in a different scenario using Docgen.

Strings are generated as "'string'" and numbers, booleans etc. as "20" or "true", so it's got nothing to do with the loader here.