* docs: Minor updates to README.md
Extension builds are now output to a `dist` folder, just like all other web packages.
* docs: Minor updates to extension README
The Firefox instructions only work in Firefox Developer Edition or Nightly
* docs: Minor fixes for CONTRIBUTING.md
Omit the quotes in the RUST_LOG value, since they cause an error on Windows and are unnecessary on other platforms.
Also clarify which debugging features are activated by RUST_LOG and which are activated only when building Ruffle with `avm_debug`.
* docs: Add detail to build instructions
Add more detailed instructions for building the desktop app, as suggested by @coreybruce in #7251