Add ComparativePieWidgetUI

[juandjara]

Description

This PR implements part of the work proposed in RFC #479

Changes added in this PR include:

• A new widget called ComparativePieWidgetUI in the widgets folder
• Typescript typings for ComparativePieWidgetUI
• JSDoc typings comments for ComparativePieWidgetUI
• Prop-types validation for ComparativePieWidgetUI
• A basic storybook story for ComparativePieWidgetUI where all prop combinations can be tested and tweaked. A screenshot of this storybook is added as visual feedback.

Type of change

• Feature

Acceptance

1. Open the local storybook running yarn storybook:start in the react-ui folder.
2. Pick a set of properties to use for testing by tweaking the storybook configuration.
3. Use this set of properties to render a ComparativePieWidgetUI in your sample project, by importing ComparativePieWidgetUI from @carto/react-ui. You can use this branch of carto-react-template to skip this step if you want, as a test screen is already setup there. Bear in mind that if this feature is not published to npm you will have to link your local version of @carto/react-* packages with yarn link.
4. Check that the rendered version of the widget in your sample project looks the same as it looks in the storybook.

Basic checklist

• Good PR name
• Shortcut link
• Changelog entry
• Just one issue per PR
• GitHub labels
• Proper status & reviewers
• Tests
• Documentation

[coveralls]

Pull Request Test Coverage Report for Build 3549580545

• 32 of 60 (53.33%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.8%) to 71.62%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/react-ui/src/widgets/comparative/ComparativePieWidgetUI.js	32	60	53.33%

Totals
Change from base Build 3494786134:	-0.8%
Covered Lines:	1879
Relevant Lines:	2434

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💛 - Coveralls

[juandjara]

@VictorVelarde test for comparative Pie Widget UI are now ready. I've added a small change to test utils to support this, let know if you find any problem with that pls.

[VictorVelarde]

Looks really nice, thx for contributing Juan!