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

- 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

web_src/css/base.css

@@ -1138,10 +1138,6 @@ overflow-menu .ui.label {
   color: var(--color-primary-contrast);
 }
 
-.activity-bar-graph-alt {
-  color: var(--color-primary-contrast);
-}
-
 .archived-icon {
   color: var(--color-secondary-dark-2) !important;
 }