[IMP] mail plugins: gmail plugin updates

[meng-odoo]

Updated to reflect how to download Gmail Plugin from Google Workspace Marketplace for Odoo Online users; added new images

Closes Odoo Task 3001713

[robodoo]

Pull request status dashboard.

[meng-odoo]

Thank you @mivu-odoo! Hi @StraubCreative, this doc is ready for your technical review. Thanks :)

[meng-odoo]

Hi @StraubCreative, I made all your requested changes. I'm still getting a failed code check that says "trailing whitespace" but I double checked every line and I don't see it. Please let me know if I should make any more changes. Thanks!

[StraubCreative]

Hi @odoo/doc-review 👋 This PR is ready for review. Please advise we couldn't find the trailing whitespace the CI check claimed was there. We combed it twice and rebased twice as well. Can you help? TIA 🙏

[Feyensv]

Hi @odoo/doc-review wave This PR is ready for review. Please advise we couldn't find the trailing whitespace the CI check claimed was there. We combed it twice and rebased twice as well. Can you help?

It means that there was some empty spaces left in your changes, though it's difficult to see unless you have a dedicated extension in your text editor:

I've removed those empty spaces and pushed an updated commit.

Note that the CI check was supposed to give the correct line where the linting error was found, which wasn't the case here, it only showed 8 instead of 88, we'll see with the runbot team to make sure it's correctly shown in the future ;).