feat: Comments to skip multiple endpoints

[Javakky-pxv]

In my product, web pages and API endpoints live together, so I need to include so many "### NoDocs ###".
To avoid this, I created a feature that allows multiple endpoints to be ignored by using "### NoDocsStart ###" and "### NoDocsEnd ###".

e.g.

### NoDocsStart ###
GET      /api/hidden/a                 controllers.hiddenEndPointA()
GET      /api/hidden/b                 controllers.hiddenEndPointB()
### NoDocsEnd ###
###
#  summary: I'm not hiding!
###
GET      /api/hidden/c                 controllers.hiddenEndPointC()

[Javakky-pxv]

Excerpt from README.

Multiple lines can be skipped.

※NoDocsEnd must always be listed directly before one line as a comment on the endpoint not to be skipped, or on the last line of the routes fill.

### NoDocsStart ###
GET      /api/hidden/a                 controllers.hiddenEndPointA()
GET      /api/hidden/b                 controllers.hiddenEndPointB()
### NoDocsEnd ###
GET      /api/hidden/c                 controllers.hiddenEndPointC()

[kailuowang]

I apologize. I thought I left a comment but obviously, I didn't actually click the comment button.
This feature will be pretty useful for sure. But I have concerns over how it's designed.
A start marker and an end marker mean that you have to track the state (like what's in between); this is extra complexity in both play-swagger code base and end-user usages. To best demonstrate this, let me use an alternative: instead of a start and end marker, we could provide an ignore whole file marker, something like

### SkipFileForDocs ###

User can put this comment at the top of the file and we can ignore the whole file. This way user won't have to worry about tracking start and end marker (e.g. accidentally delete or add an extra marker that breaks the pair). Code in play-swagger might be simpler as well.
That being said, I don't actually know if it's easier for you to skip the whole file. If that's not the case maybe we have to go this route.

[Javakky-pxv]

@kailuowang
I don't want to be forced to split my routes file! On the other hand, I feel that it would be possible to semantically separate APIs that need to be documented from those that do not.
I'll try @kailuowang's idea first and see how it works before I submit this pull request.