maint(deps-dev): bump rollup from 2.79.0 to 3.20.2 (#358)

Bumps [rollup](https://github.com/rollup/rollup) from 2.79.0 to 3.20.2.

The only difference in artifacts is in the CJS file. The dynamic import of superagent is no longer rewritten as require (rollup/rollup#4647). We can turn that off with rollup config, but it should work with this change since dynamic import in CJS has been available since node version 9.

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -46,7 +46,7 @@
     "jest-in-case": "^1.0.2",
     "prettier": "^2.3.1",
     "regenerator-runtime": "^0.13.9",
-    "rollup": "^2.58.0",
+    "rollup": "^3.20.2",
     "superagent-mocker": "^0.5.2"
   },
   "dependencies": {