Checkbox, Radio Button, and Fieldset Components

[natalynyu]

This PR adds the Checkbox, RadioButton, and Fieldset components. The styling is based off of Vittorio Bucchieri's recommendations. As a note, a fieldset is required to be used in conjunction with both checkboxes and radio buttons for accessibility reasons.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have run eslint on the code
• [x] I have added JSDoc for all of my code (where applicable)
• [x] I have added tests to cover my changes.

Priority:

• [x] Normal
• [ ] High

Related Issues:

Addresses #229

[codecov[bot]]

Codecov Report

Merging #72 into develop will decrease coverage by 1.32%. The diff coverage is 98.82%.

@@             Coverage Diff             @@
##           develop      #72      +/-   ##
===========================================
- Coverage   100.00%   98.67%   -1.33%     
===========================================
  Files           34       41       +7     
  Lines          429      530     +101     
  Branches        50       98      +48     
===========================================
+ Hits           429      523      +94     
- Misses           0        4       +4     
- Partials         0        3       +3     

Impacted Files	Coverage Δ
src/Forms/RadioButton.tsx	91.66% <91.66%> (ø)
src/Buttons/BorderlessButton.tsx	100.00% <100.00%> (ø)
src/Buttons/Button.tsx	100.00% <100.00%> (ø)
src/Forms/Checkbox.tsx	100.00% <100.00%> (ø)
src/Forms/Dropdown.tsx	100.00% <100.00%> (ø)
src/Forms/Fieldset.tsx	100.00% <100.00%> (ø)
src/Forms/Label.tsx	100.00% <100.00%> (ø)
src/Forms/TextInput.tsx	100.00% <100.00%> (ø)
src/Forms/ValidationErrorMessage.tsx	100.00% <100.00%> (ø)
src/Forms/index.ts	100.00% <100.00%> (ø)
... and 39 more

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[natalynyu]

I reorganized the tests so that there is a describe block for each prop and removed tests that were not affected by that specific prop. (commit 78434c9).

[rmainwork]

LGTM. Approved.