Update README.md

[dshemetov]

Checklist

Please:

• [x] Make sure this PR is against "dev", not "main" (unless this is a release PR).
• [x] Request a review from one of the current epidatr main reviewers: brookslogan, dshemetov, nmdefries, dsweber2.
• [x] Makes sure to bump the version number in DESCRIPTION. Always increment the patch version number (the third number), unless you are making a release PR from dev to main, in which case increment the minor version number (the second number).
• [x] Describe changes made in NEWS.md, making sure breaking changes (backwards-incompatible changes to the documented interface) are noted. Collect the changes under the next release number (e.g. if you are on 1.7.2, then write your changes under the 1.8 heading).

Change explanations for reviewer

Add link to the CRAN page.

Magic GitHub syntax to mark associated Issue(s) as resolved when this is merged into the default branch

[dsweber2]

This should be updated in the Rmd, not the md, otherwise it'll just get overwritten

[dshemetov]

Gonna add this to your other PR.