Allow for esbuild configuration

[erikm-icario]

I made a change to Serverless Stack's (https://github.com/serverless-stack/serverless-stack) Function construct so that the nodejs bundling process ran an esbuild script file that merges options set by the construct with a loaded configuration instead of calling esbuild directly. This enabled things like plugins while bundling the functions. I use this for decorator metadata.

It doesn't seem like there's any reason why this approach couldn't be done with the existing nodejs lambda construct. That would be nice because I can then also benefit from the Docker bundling, which Serverless Stack's Function forgoes.

The approach seems pretty simple:

• Change the bundling step to base64 encode the configuration and call the script instead of esbuild with the configuration and the location of the esbuild config script
• Create the script to merge the decoded configuration and the loaded configuration file then run esbuild
• Update the docker file to call the script

This approach should work for local and docker bundling if done correctly.

I took a stab at this but ran into some issues running/testing it.

There are also some questions:

• What's the best way to get the necessary files/configuration/parameters inside the docker container?
• How should the location of the esbuild configuration be picked up by the nodejs lambda construct?