Redesign the contribution analytics graphs

app/assets/javascripts/vue_shared/components/bar_chart.vue

.../javascripts/vue_shared/components/bar_chart_constants.js

...assets/javascripts/vue_shared/components/svg_gradient.vue

app/assets/stylesheets/pages/graph.scss

...p/assets/javascripts/pages/groups/analytics/show/index.js

ee/app/views/groups/analytics/show.html.haml

...hangelogs/unreleased/jivl-redesign-contributors-graph.yml

package.json

spec/javascripts/vue_shared/components/bar_chart_spec.js

yarn.lock