Allow the location for gatsby-types.d.ts to be configured

[nrandell]

It would be great to be able to provide a configuration option to write the gatsby-types.d.ts in another location. There are a few reasons for doing this

• in case something else detects the file being created and creates an infinite loop in the build (eg tailwind)
• when you don't want that file added to git and keeping it out of the src folder is useful

Using the new file is a simple matter of adding it to tsconfig.json and everything would continue to work correctly.

[zhaohuanyuu]

i have the same question(tailwind loop), hope solved soon

[LekoArts]

PR for it is up now: #35966

You can try this now with gatsby@next or wait for 4.18 release.