Feature: embed required deps via a embed file that is behind a unused build flag

[Waldeedle]

Basically by creating an embed go file, go recognizes the dependencies and downloads them along with the lilliput library code.
By using a build flag, that isn't actually called at build time, the embed.go file is not added so nothing is actually being embedded into the binary.

This downloads the deps for both linux and mac (tested on m1 and linux containers). I wonder if we could be fancy with the OS and download only the OS specific ones but this was sufficient for my use-case

closes #195

[Waldeedle]

here is an example when using go's native dependency commands with my changes (in my case using go mod tidy and go mod vendor)

You can test this on any existing go project. The only change is needed in the go.mod file to point at my branch's commit in order to have it pull everything in.

replace github.com/discord/lilliput => github.com/waldeedle/lilliput v0.0.0-20250318230505-240ed26e1aff

[skidder]

Looks good, thanks for the PR!