Use esbuild's cssBundle for getting the appropreate css bundle instead of relying on regex to find path

[craftamap]

In the latest version of esbuild (v0.15.10), a link to the css bundle was added to the metafile. Currently, we are using a quite hacky way to figure out which css file is used. This change should enable us getting rid of (or at least comment out) the current detection.