How to install a specific file as part of a plugin to the build output folder?

[dleetr]

I'm trying to migrate a plugin to be snowpack3 compatible. There is a problem where the file is copied but then cleaned by snowpack itself. I am unsure of which lifecycle hook I can utilize to trigger this copying at the correct time so that it does not get cleaned. The easiest solution I've found thus far is to simply disable the cleaning process, but that isn't an ideal solution. Note that this plugin functioned fine for snowpack 2

Plugin Issue:
AWolf81/snowpack-plugin-web-ext#6

The problem seems to occur directly after this line, I'm not sure if it's a bug of snowpack or something else:
const content = await fsPromise.readFile(packageJsonPath, { encoding: "utf8" });
https://github.com/AWolf81/snowpack-plugin-web-ext/blob/main/src/config.ts#L28