feat: add --stdio flag

[danielpza]

Closes #4

Adds two new flags:

• --stdio - read from stdin and write to stdout
• --file-path - file location to use for --stdio source code

example:

ts-import-types --stdio --file-path src/index.ts < src/index.ts > out.ts

[danielpza]

Hey @JamieMason, hope you are doing well.

Any chance this can be merged?

Cheers.
Daniel