feat(cv-progress-skeleton): add initial implementation

[mateusbandeiraa]

Contributes to #167

## What did you do?
Implemented cv-progress-skeleton.

## Why did you do it?
Because Carbon Vue rocks 😄 . And it was requested on #167.

How have you tested it?

Ran the existing unit tests and added new ones.

Were docs updated if needed?

• N/A
• No
• Yes

[mateusbandeiraa]

There's an annoying bug on this implementation that I temporarily fixed in an ugly way-- I don't even know if this could be
merged like this.

The label skeletons are not vertically aligned with the circle icons.

But the current React implementation looks good:

It looks like a bug on carbon-components that was fixed on version v11.38.0:
carbon-design-system/carbon@abff3a5#diff-275e913cf6a488e64f5011914882d9af6e9b614c918bb82f81990c7d3e147fd2L27-R27

I "fixed" it on my side by adding this style (not included on the PR):

<style scoped>
.bx--progress--vertical .bx--progress-label {
  margin-block-start: 0;
}
</style>

[davidnixon]

I think this is OK as-is. When we upgrade the components to Carbon 11 the alignment will get fixed.

[mateusbandeiraa]

Alright. Marked as ready for review.