`embedding-sdk:dev`: --watch that makes "fixed" dts (#48574)

* faster --watch command for the sdk

* apparently we want an empty line at the end of jsons, but prettier removes it?

* format tasks.json with prettier 

* vscods tasks, move watch task from webpack config to the fixup script

* cleanup webpack config

* adds clean + waits for dist folder when not existing

* minimal doc for the sdk commands