lll: ignore comments containing only URL

[ldez]

As illustrated in the following example, to ignore long URLs the nolint directive should be placed on the top of the comments but this ignores lll on the whole function.

.golangci.yml

linters:
  disable-all: true
  enable:
    - lll
    - typecheck

linters-settings:
  lll:
    line-length: 50

package main

import "fmt"

// main runs the app.
// https://github.com/walle/lll/blob/4438bccd245f7e87a5a69023625f01e7035c05c0/utils.go#L15
//
//nolint:lll
func main() {
	fmt.Println("Foo")
}

$ golangci-lint run 
$

Fixes #3983

[mattdowdell]

Would it be possible to also exclude URLs used as reference links? e.g.

Here's a [link] and [another][1]!

[link]: https://example.com
[1]: https://example.com

I sometimes use these references to keep Go docs readable when browsing code (inserting long URLs makes following text hard), and given modern godoc uses markdown, this would likely be universally helpful.

[batazor]

Sometimes in the code you have to leave links to tasks in the tracker or links to discussion of some bugs - to understand why it was done this way.

And often they are long links, it would be cool to be able to skip such cases by default.