Make the readme cut-off hint more visible

[mk-pmb]

Problem description

As mentioned in "5000 character limit on descriptions" (#238), where it was suggested that closed tickets are rarely read:

I usually skim manuals for the relevant parts, so at first I missed the cut-off note on top of https://hub.docker.com/_/postgres . My first idea was: Can we please repeat that note directly below the actual cut-off? And can we give that note a box layout, at least a border?

Looking further, I got the impression that the current implementation might be one where the hint eats into the character count available for the actual readme, and that a box markup would increase this cost. If so, I suggest we just add […] (see hint at start of readme) to the end.

We should ensure that if the cut-off happens inside an HTML comment, that comment is removed entirely. Due to the character limit, it would even seem useful to ensure we strip ALL comments upfront.

Task List

• [x] This is NOT a security issue
• [x] I do NOT have a Docker subscription
• [x] I have looked through other issues and they do NOT apply to me

[tianon]

I've got a first pass at implementing this up in https://github.com/docker-library/docs/pull/2129 :+1:

[tianon]

I think this can be closed (thanks to https://github.com/docker-library/docs/pull/2129).