some small improvements to the data explorer webpage

[nevrome]

Motivated by a comment of @KathrinNaegele I did some work on the html API this weekend.

As suggested by @stschiff in #333, I ...

• added per-archive lists of last-modified packages to the main page
• added the last-modified dates for each package in the package table on the archive page
• made the package and individual lists dynamic and sortable with a new dependency on simple-datatables (essentially DataTables without jQuery)

I haven't tested this yet with the Poseidon server production setup.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 33 lines in your changes missing coverage. Please review.

Project coverage is 55.55%. Comparing base (d0c7b34) to head (3a58923).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Poseidon/ServerHTML.hs	0.00%	33 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #341      +/-   ##
==========================================
- Coverage   55.75%   55.55%   -0.20%     
==========================================
  Files          31       31              
  Lines        4744     4761      +17     
  Branches      510      510              
==========================================
  Hits         2645     2645              
- Misses       1589     1606      +17     
  Partials      510      510              

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[stschiff]

Great, I'll take a look later, shouldn't take too long

[stschiff]

Great, I've quickly tested it locally. Seems to all work as expected. Thanks.

[stschiff]

Note that CI fails. Note sure what exactly though.