This is a two-step-process:

1. Create a webpack/vue-cli configuration that compiles src/app as a standalone library. Use webpack/vue-cli instead of browserify in the Gulpfile.
2. redefine donationForm and membershipForm as entry points (requiring/importing specific items from src/app). Bundle jQuery and jcf as vendor.js, declaring them as external for all the other scripts in scripts.

If you also want to build the FAQ with webpack, you might have to create different webpack configurations, as the library configuration for the output must not be in the FAQ configuration and output can't be configured on a per-entrypoint basis.