feat: add Robot Framework support

[jpbernius]

Add support for Robot Framework files with its two file extensions .robot and .resource.

See https://robotframework.org/robotframework/latest/RobotFrameworkUserGuide.html#supported-file-formats

[jpbernius]

I am exploring a dedicated header style for Robot Framework to support the *** Comments *** section layout which is recommended and also enforced by their linter. I will reopen this PR later with its own header style definition.

[tisonkun]

Thanks for reaching out and feel free to open a PR anytime when it is ready.

One concern I may have is that .resource can be too common to conflict with unrelated files. Perhaps you can consider extensions like .robot.resource in the flavor of .config.js.