[PostGIS] #5888: Add packaging status badge/links from Repology

[PostGIS]

#5888: Add packaging status badge/links from Repology
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  Reporter:  strk        |      Owner:  robe
      Type:  task        |     Status:  new
  Priority:  low         |  Milestone:  Website Management, Bots
 Component:  management  |    Version:
Resolution:              |   Keywords:
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Comment (by strk):

 I've added a link in the wiki (no badge, just link):
 https://trac.osgeo.org/postgis/wiki#Downloading
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5888#comment:1>
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