dev-cmd/contributions: Add a per-repo total column to the CSV

```
$ brew contributions issyl0 --csv
The user issyl0 has made 1202 contributions in all time.
user,repo,commits,coauthorships,signoffs,total
issyl0,brew,332,13,0,345
issyl0,core,473,24,326,823
issyl0,cask,4,0,0,4
issyl0,aliases,0,0,0,0
issyl0,autoupdate,1,0,0,1
issyl0,bundle,14,2,0,16
issyl0,command-not-found,1,0,0,1
issyl0,test-bot,3,0,0,3
issyl0,services,9,0,0,9
issyl0,cask-drivers,0,0,0,0
issyl0,cask-fonts,0,0,0,0
issyl0,cask-versions,0,0,0,0
```

Library/Homebrew/dev-cmd/contributions.rb

@@ -96,9 +96,16 @@ module Homebrew
   sig { params(user: String, results: Hash).returns(String) }
   def generate_csv(user, results)
     CSV.generate do |csv|
-      csv << %w[user repo commits coauthorships signoffs]
+      csv << %w[user repo commits coauthorships signoffs total]
       results.each do |repo, counts|
-        csv << [user, repo, counts[:commits], counts[:coauthorships], counts[:signoffs]]
+        csv << [
+          user,
+          repo,
+          counts[:commits],
+          counts[:coauthorships],
+          counts[:signoffs],
+          counts.values.sum
+        ]
       end
     end
   end