test(storybook): implement storyshots snapshot testing

[DianaLease]

Signed-off-by: Diana Lease [email protected]

Changes

• test(storybook): implement storyshots snapshot testing
• refactor(*): removes unused files from boilerplate code

Flags

• Using v6.0.0-alpha version of storyshots because it fixes an issue where storyshots did not work for stories using React hooks (see [Addon-storyshots] Hooks in story break tests storybookjs/storybook#8177). I favored using the alpha pre-release over using the "hack".

[jolanglinais]

My impression is this would be a first step towards #14, which will be the real substance of the testing.