[UI] Replace vue-bar-graph with chart.js

- Backport of #4571
- The usage of the `vue-bar-graph` is complicated, because of the `GSAP`
dependency they pull in, the dependency uses a non-free license.
- The code is rewritten to use the `chart.js` library, which is already
used to draw other charts in the activity tab. Due to the limitation of
`chart.js`, we have to create a plugin in order to have images as labels
and do click handling for those images.
- The chart isn't the same as the previous one, once again simply due to
how `chart.js` works, the amount of commits isn't drawn anymore in the
bar, you instead have to hover over it or look at the y-axis.
- Resolves #4569

(cherry picked from commit a83002679d)

templates/repo/pulse.tmpl

@@ -101,7 +101,7 @@
 				<strong class="text red">{{ctx.Locale.TrN .Activity.Code.Deletions "repo.activity.git_stats_deletion_1" "repo.activity.git_stats_deletion_n" .Activity.Code.Deletions}}</strong>.
 			</div>
 			<div class="ui attached segment">
-				<div id="repo-activity-top-authors-chart"></div>
+				<div id="repo-activity-top-authors-chart" data-locale-commit-activity="{{ctx.Locale.Tr "repo.activity.commit"}}"></div>
 			</div>
 		</div>
 	{{end}}