MR Analytics - Add throughput charts to storybook

Background

While discussing some options for improvements to some existing charts, it was noticed that the current charts for groupoptimize arent very straightforward to experiment and interact with.

Related to &11681

Proposal

• Add a story file for the merge request analytics throughput_charts
• Add a story file for the merge request analytics throughput_stats
• Add a story file for the merge request analytics throughput_table

Implementation guide

• Add a new story file named throughput_chart.stories.js for the throughput_chart.vue component
  • The default story should render the chart with data
  • Add a story for the chart without any data available
  • Add a story for the chart in the loading state
• Add a new story file named throughput_table.stories.js for the throughput_table.vue component
  • The default story should render the table with data
  • Add a story for the table without any data available
• Add a new story file named throughput_stats.stories.js for the throughput_stats.vue component
  • The default story should render the table with data
  • Add a story for the stats in the loading state
• This chart and table use graphql so we can use the createVueApollo method provided in the story context to provide data

Take a look at the type_of_work_charts.stories.js file for some inspiration