Add a config option to control tactics' auto's gas

[isovector]

It would allow us to solve things like #562

[isovector]

Additionally, maybe automatically increase the gas if a hole fill doesn't produce any results.

[jneira]

Only want to note that now plugins has its own namespace in our config: #691

[isovector]

Thanks for the info, @jneira . Do these options show up in editors' configuration settings?

[jneira]

I am afraid they still not are, there is an issue about haskell/vscode-haskell#336
You can do it manually though: #1342 (comment)