Running from source instructions improvements

[davidfraser]

I have been making some changes to aw-webui. The instructions in the README say to copy the web assets to the main install.

However, at least on Windows, aw-server-rust seems to bundle the static data inside the executable. Replacing the static/ directory didn't seem to do anything. But there is a command-line flag --webpath that allows loading the webui from another location. The following worked for me:

• Running aw-server-rust.exe --webpath \path\to\aw-webui\dist
• Copying dist over static and running aw-server-rust.exe --webpath static

Could this be adjusted in the instructions?