Update dependencies and migrate to Scala 2.13

[hlxid]

Description

We haven't really bother updating our dependencies till this point, but we should start doing that somewhat regularly. Here are the currently available updates:

Found 12 dependency updates for chatoverflow
  com.fazecast:jSerialComm                 : 2.5.1           -> 2.5.3                                      
  com.github.scopt:scopt                   : 3.5.0                               -> 3.7.1                  
  com.google.code.gson:gson                : 2.8.5           -> 2.8.6                                      
  com.typesafe.akka:akka-actor             : 2.5.18          -> 2.5.27           -> 2.6.1                  
  io.get-coursier:coursier                 : 2.0.0-RC3-2     -> 2.0.0-RC5-4                                  
  net.dv8tion:JDA                          : 3.8.3_463       -> 3.8.3_464                  -> 4.1.0_90     
  org.json4s:json4s-jackson                : 3.5.2           -> 3.5.5            -> 3.6.7                          
  org.scalatra:scalatra-json               : 2.6.3           -> 2.6.5                                      
  org.slf4j:slf4j-log4j12                  : 1.7.22          -> 1.7.30 
Found 4 dependency updates for chatoverflow-launcher-updater
  com.github.scopt:scopt       : 3.5.0             -> 3.7.1 
  me.tongfei:progressbar       : 0.7.4             -> 0.8.0 
  org.json4s:json4s-jackson    : 3.5.2  -> 3.5.5   -> 3.6.7 
Found 3 dependency updates for chatoverflow-launcher-bootstrap
  com.github.scopt:scopt       : 3.5.0                      -> 3.7.1 
  io.get-coursier:coursier     : 2.0.0-RC3-2 -> 2.0.0-RC5-4          

Since some are quite old and we don't have any tests yet we need to particularly check that they don't break any of our functionality.
There is also sbt which can be upgraded from 1.1.2 to 1.3.6 and we should upgrade to Scala 2.13 if all our scala dependencies are also available for it.

In the future we could also automate this through e.g. scala-steward.

[hlxid]

We'll need to postpone the Scala 2.13 migration because Scalatra isn't yet released for Scala 2.13. Let's hope that it doesn't take too long. Sbt and dependency upgrades have been merged.