fix extension resolving for esbuild

[mansona]

We have implemented extension searching on the Vite side of a build, but in #1779 our templates are starting to get analysed in esbuild and need the same "extension candidate" implementation 👍

[patricklx]

i'm not sure what changed, but vite adds its own plugin to esbuild:vite:dep-scan, which then calls all vite plugins. So it should go through vite/src/hbs.ts etc
and currently it also goes into build.onLoad({ filter: /\.g[jt]s$/ }, async ({ path: filename })...

[patricklx]

this could also be fixed by setting the extensions resolving in vite config.

https://vitejs.dev/config/shared-options#resolve-extensions

which would also need to be done for rollup with an extra plugin...

[ef4]

We discussed this and @patricklx's questions are good ones. We think vite does not add custom rollup plugins to the esbuild when doing dep pre-building. We can probably rely on resolve-extensions for gjs and gts, but the hbs rollup plugin has more complex behaviors. We can experiment with slightly simplifying our plugins in favor of resolve-extensions but it would not completely replace them.