Fix no build before npm publish

[pplancq]

Hello @bencompton ,

Sorry for the direct mention, but there's a big problem with the github publish action. The build step is missing, which means the dist folder isn't published to the npm registry.
This makes the library unusable.

I suggest this quick fix to quickly fix and republish a patched version.

[bencompton]

Thanks a bunch for catching this! I tested 4.0.1 in another project, but now that I double check, it was still using the previous version. 🤦

[pplancq]

No problem, to err is human as they say.
On the other hand, I notice that you didn't release 4.0.2 on the master.