[metrics-bugs] #23830 [Metrics/Website]: Update README to get a development environment for metrics-web going

[Tor Bug Tracker & Wiki]

#23830: Update README to get a development environment for metrics-web going
-----------------------------+------------------------------
 Reporter:  irl              |          Owner:  metrics-team
     Type:  enhancement      |         Status:  new
 Priority:  Medium           |      Milestone:
Component:  Metrics/Website  |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:                   |  Actual Points:
Parent ID:                   |         Points:
 Reviewer:                   |        Sponsor:
-----------------------------+------------------------------

Comment (by irl):

 I found that I also required `tomcat8-annotations-api-8.5.24.jar` but this
 may be due to me using different versions on Debian testing. Next year
 I'll get a Debian stable virtual machine set up for doing
 development/testing on.

 I also had to disable `duplicate="fail"` for the war target in the ant
 script. This is probably suboptimal although I don't really understand
 what that does. Maybe it's only working for me by chance.

 Other than that, using iwakeh's `task-24175-stepbystep` branch, I was able
 to set up a development instance! (:

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23830#comment:10>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online