Node v10 compatibility

[jeffposnick]

v2.x of this module fixed a security vulnerability by updating its ejs dependency. It also started using String.prototype.matchAll(), which isn't compatible with Node v10:

rollup-plugin-off-main-thread/index.js

Line 102 in c967772

for (const match of code.matchAll(workerRegexpForTransform)) {

I'm not sure if this was intentional or not, as there's no minimum support Node engine version listed in your package.json, and I can't find any release notes for v2.x of this module.

The Workbox project would like to update its dependency on this module, but we need to continue support Node v10 until our next major release version.

Would you be open to a PR that swapped out matchAll() for the equivalent, so that a version of this module with the updated ejs dependency could be used with Node v10?