Add a .readthedocs.yml configuration file

[jhedstrom]

See https://blog.readthedocs.com/migrate-configuration-v2/

[SamantaTarun]

I'd like to work on it.

[jhedstrom]

@tarunsamanta2k20 please do! I think if you just add the basic config file from that link in a PR it should work. There's also the issue over at jhedstrom/DrupalDriver#266 if you want to do the same there!

[SamantaTarun]

@jhedstrom I have already added that file. Have you reviewed my commit?

[jhedstrom]

@tarunsamanta2k20 I missed that entirely :) Thanks for working on that!