Add documentation for the Google Analytics import

[m-col]

This adds docs for the Google Analytics import feature. The following
changes are included:

• A dedicated page on the feature aimed at users in the Website Settings
  section.
• Mention of removing imported data in the 'Reset your site data' and
  'Delete your site data' pages.
• A note on the filter-segments page informing the reader that imported
  data is not included when querying filtered data.
• Inclusion of imported data in the Stats API reference.
• Steps in the self-hosting docs for enabling the feature in Plausible.

--

I think I've covered all bases throughout the docs, but let me know if you think anything else needs adding!

[m-col]

AFAICT the check failures are unrelated:

12:48:48 PM: error @docusaurus/core@2.0.0-beta.14: The engine "node" is incompatible with this module. Expected version ">=14". Got "10.24.1"
12:48:48 PM: error Found incompatible module.
12:48:48 PM: info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
12:48:48 PM: Error during Yarn install
12:48:48 PM: Build was terminated: Build script returned non-zero exit code: 1

[metmarkosaric]

nice, thanks @m-col! looks great on the first review. i'll take a closer look and merge it all when we start getting the import ready for launch.

[ukutaht]

@metmarkosaric can this be closed? I think we have docs for this right?

[metmarkosaric]

@metmarkosaric can this be closed? I think we have docs for this right?

it includes some changes to the self-hosted docs around the GA import too. is there a way to just merge the changes to docs/self-hosting-configuration.md and ignore everything else?

[ukutaht]

Yeah I'll do it when we release self-hosted