lint

nimlint makes developing softer.

Ref timotheecour/Nim#415

lint items

• code block => runnableExamples
• proc + noSideEffect => func
• assert in a test file => doAssert
• isMainModule in stdlib => recommend moving to tests/stdlib/tfoo.nim
• double backticks => single backticks
• the first char should be upper

TODO

• Better messages with filename, line and col number
• Github APP integration ➡️ https://github.com/juancarlospaco/nimlint-action
• Fix them
• Syntax to ignore lint recommendations, analog to #!nimpretty off (maybe via a pragma or special #!nimlint:off syntax)