fix(gatsby): show theme that has faulty config

[mxstbr]

When a user uses a theme that has a invalid plugin configuration in its gatsby-config.js, the user will see a blocking error:

❯ GATSBY_EXPERIMENTAL_PLUGIN_OPTION_VALIDATION=true yarn start
yarn run v1.22.4
$ gatsby develop

success open and validate gatsby-configs - 0.064s

 ERROR #11331  PLUGIN

Invalid plugin options for "gatsby-plugin-mdx":

- "plugins" must contain 0 items

not finished load plugins - 3.026s
error Command failed with exit code 1.

However, the user doesn't even have gatsby-plugin-mdx in their gatsby-config and cannot fix this since they might not have control over the theme that incorrectly uses this plugin! 😱

This patch fixes that case by instead 1) logging the directory of the faulty gatsby-config and 2) not blocking yarn develop if the error is from a gatsby-config outside the users root directory.

Now, it looks like this:

❯ GATSBY_EXPERIMENTAL_PLUGIN_OPTION_VALIDATION=true yarn start
yarn run v1.22.4
$ gatsby develop

Something is already running at port 8000
✔ Would you like to run the app at another port instead? … yes
success open and validate gatsby-configs - 0.073s
⠀
 ERROR #11331  PLUGIN

Invalid plugin options for "gatsby-plugin-mdx", configured by node_modules/@lekoarts/gatsby-theme-minimal-blog-core:

- "plugins" must contain 0 items

success load plugins - 0.892s
success onPreInit - 0.029s
success initialize cache - 0.026s
success copy gatsby files - 0.048s
success onPreBootstrap - 0.015s
success createSchemaCustomization - 0.010s
...etc...

This makes sure we don't block the user with errors they don't have control over.

[wardpeet]

Shouldn't we kill the process? If a theme has a bad config, the site will probably have funky behavior or error out eventually. I think it's best to die anyway

[mxstbr]

I don't think so, users literally cannot change it in most cases when they use a third-party theme. 🤔 I don't want to block anyone from using a theme even if it uses configuration that doesn't match the schema...