[metrics-bugs] #23348 [Metrics/Onionoo]: update all documentation md-files

[Tor Bug Tracker & Wiki]

#23348: update all documentation md-files
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     Reporter:  iwakeh           |      Owner:  metrics-team
         Type:  enhancement      |     Status:  new
     Priority:  Medium           |  Milestone:  Onionoo-1.4.0
    Component:  Metrics/Onionoo  |    Version:
     Severity:  Normal           |   Keywords:
Actual Points:                   |  Parent ID:
       Points:                   |   Reviewer:
      Sponsor:                   |
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 Mostly, remove outdated info and provide appropriate links to Metrics
 development and contribution wiki pages.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23348>
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