Auto merge PRs to DT

[Maxim-Mazurok]

As per conversation with @orta:

DT merge-bot logic is here: https://github.com/DefinitelyTyped/dt-mergebot

if you arbitrarily change a single test file you can get it easier to auto-merge

You'll need the bot to also say "OK to merge" or something like that after CI (~1 hr) too
Perhaps make an issue on https://github.com/DefinitelyTyped/dt-mergebot/issues about asking for a way to declare that some modules are auto generated

So, we have to:

• add change to tests (probably, revision number) - this actually seems optional
• create second GH account that will open these PRs (to get hasFinalApproval and Merge:Auto)
• respond to bot request to auto-merge (post Ready to merge from @Maxim-Mazurok )

[Maxim-Mazurok]

Please, welcome our bot: @google-api-typings-generator :) #281 will use this account.
Its profile picture should not conflict with Google Logos and Trademarks Usage Guidelines, because it uses a distinctly different font and color for G.
Also, it follows TS branding guidelines: we don't use TS logo in any form, just the "TypeScript Blue" color.

[Maxim-Mazurok]

add change to tests (probably, revision number)

Done in #339