Remove skeleton comments

[NickSdot]

In php/doc-en#5630 we decided to remove these comments, and mention PER instead of PECL; this PR aligns the doc-base skeletons to that decision.

Additionally
I added todo markers to PECL references in the skeleton directory (second commit). Since PECL is deprecated in favour of PIE, we should think about what to do with these - I'd appreciate your input to that! Marked as draft for now -- before the merge the second comments should either be dropped, or a follow up commit be made for whatever you imagine to happen with the PECL mentions.

[kamil-tekiela]

If we decide that we no longer allow PECL in the manual then the skeletons can be updated. I don't know who is using the skeletons and for what, but as of now, PECL extensions are still documented in the PHP manual. Either way it's a distinct change from removal of the editor fence comments.

[NickSdot]

> but as of now, PECL extensions are still documented

But no new docs added. So why would the skeleton/templates keep it?

Edit:

If we decide that we no longer allow PECL in the manual then the skeletons can be updated. I don't know who is using the skeletons and for what, but as of now, PECL extensions are still documented in the PHP manual. Either way it's a distinct change from removal of the editor fence comments.

You are right, having this discussion mixed in here doesn't make sense. I opened #310

[kamil-tekiela]

Ok. But I don't know know if we should have these skeletons.

[NickSdot]

Ok. But I don't know know if we should have these skeletons.

Personally I found them helpful to get an idea for what is available without checking individual docs pages -- as in having a full overview at a glance.