Add a .editorconfig file

[mhucka]

Is your feature request related to a use case or problem? Please describe.

To help developers more easily write code that fits the project coding style, and to reduce time spent correcting formatting discrepancies that get flagged by code checkers, we should probably add a .editorconfig file.

Describe the solution you'd like

Create a .editorconfig file at the project top level, and set it up to match what is required by check/all.

[optional] Describe alternatives/workarounds you've considered

We could point people to a style guideline document and let them take care of setting things up themselves. This is more flexible but less efficient and effective than providing a configuration file.

What is the urgency from your perspective for this issue? Is it blocking important work?

P2 - we should do it in the next couple of quarters

We are already having cases of discrepancies between people's editors and what the Black-based formatting checks in Cirq complain about, so this is a real need.

[mhucka]

I found this .editorconfig in qh-lab. Perhaps this can be a starting point?

root = true

[*]
charset = utf-8
end_of_line = lf
insert_final_newline = true
trim_trailing_whitespace = true

[*.py]
indent_size = 4
indent_style = space
max_line_length = 100

[*.sh]
indent_size = 4
indent_style = space
max_line_length = 100