CI: run FSharpLint on itself

[knocte]

Nits on commit messages:

FSharpLint.Core: Resolve pascalcase consideration

Use lowercase after ':'.

build.yml: run Fsharplint on itself

Rather use CI as scope, not build.yml; also please capitalize FSharpLint properly.

FSharpLint.Core: apply lint warnings

Rather 'respect our own lint rules'.

After you have fixed commit msgs, push, and after that, please rebase your branch.

[knocte]

2 things:

• You forgot to push 1by1.
• Last commit's CI is broken, please fix.

[Mersho]

Closed in favor of https://github.com/fsprojects/FSharpLint/pull/628