fix(checkbox): enable name attribute

[nicklasisraelsson]

This is a suggested interim solution until issue #438 can be resolved to be able to use Checkbox components in forms.

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here (e.g. I signed it!) and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

Googlers can find more info about SignCLA and this PR by following this link.

[codecov-io]

Codecov Report

Merging #678 into rc0.10.0 will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##           rc0.10.0     #678      +/-   ##
============================================
+ Coverage     94.88%   94.88%   +<.01%     
============================================
  Files            68       68              
  Lines          2852     2853       +1     
  Branches        432      432              
============================================
+ Hits           2706     2707       +1     
  Misses           50       50              
  Partials         96       96

Impacted Files	Coverage Δ
packages/checkbox/index.tsx	89.33% <100%> (+0.14%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 02da75c...57ba49d. Read the comment docs.

[nicklasisraelsson]

I signed it!

[moog16]

looks good - thanks for adding a test.

[moog16]

cla not passing - signed in #678 (comment)