Enable permissive max-len and max-lines as warning

[fregante]

• Closes Reintroduce "length" rules to catch excess xo#738

I think it might make sense to enable them as warning to look at the pushback without creating too much trouble.

I think 200ch is a good upper limit, but I'm not sure about "1000 lines", especially in files with inline documentation and licensing.

[sindresorhus]

I think 2000 lines is too little.

[fregante]

The point of this warning is to push people to split up larger files. Even you reach the limit, you can just disable it in the file, hopefully as an exception rather than a common occurrence.

2000-lines is already excessive to me, but it could be a start to verify any pushback.