docs(readme): update grammar

[ksb86]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

[welcome]

Thanks for opening a pull request!

Here are some highlighted action items that will help get it across the finish line, from the
pull request guidelines:

• Follow the JavaScript coding style.
• Run npm run lint locally to catch formatting errors earlier.
• Document any user-facing changes in NEWS.md and other docs.
• Include tests when adding/changing behavior.

Development and triage is community-driven, so please be patient and we will get back to you as soon as we can.

[codecov]

Codecov Report

Merging #1227 (6406a7b) into master (0d3f843) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master     #1227   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           14        14           
  Lines          698       698           
=========================================
  Hits           698       698           

---

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 0d3f843...6406a7b. Read the comment docs.

[welcome]

Thanks for your contribution! 🎉