WEB: Sort PDEPs by their number
Sort PDEPs by their number rather than the title. 

- [x] closes #51662  

@datapythonista thx for review. New commit has the suggested changes. > @datapythonista thx for review. New commit has the suggested changes.

@datapythonista being a pest :) > Thanks @kostyafarber, very nice. Looks great, my only concern is that if one of the sorted issues doesn't use `PDEP-\d...` as the title, I think this will fail with an error difficult to debug. I'm in my phone and can't check in detail, but let me know if I'm wrong. If I'm correct, maybe we can move the lambda to a function (can be inside the same function) and raise our own exception and error message when the pattern is not found. Thanks!

No worries, I think that's a sensible concern, I'll investigate and let you know. @datapythonista re-wrote to raise when we don't get a match with (useful) msg. Cheers @datapythonista friendly ping.  /preview Website preview of this PR available at: https://pandas.pydata.org/preview/52072/ Thanks @kostyafarber 