document exporters as installable packages

[brettmc]

Exporters can be individually installed via packagist now, so link to them. Also add the exporter tag to some exporters that were missed, so they can be found more easily.

[codecov]

Codecov Report

Merging #817 (536bd57) into main (ac3a35d) will not change coverage.
The diff coverage is n/a.

❗ Current head 536bd57 differs from pull request most recent head b910869. Consider uploading reports for the commit b910869 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #817   +/-   ##
=========================================
  Coverage     82.88%   82.88%           
  Complexity     1829     1829           
=========================================
  Files           225      225           
  Lines          4697     4697           
=========================================
  Hits           3893     3893           
  Misses          804      804           

Flag	Coverage Δ
7.4	82.89% <ø> (ø)
8.0	?
8.1	82.91% <ø> (ø)

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