v1.7.0-beta.0

We're rather behind and will continue to be behind, so we're tagging a beta release as a stopgap for people who want the new features.

Notable things: unsandboxed extensions, rename broadcasts, automatic extension loading

The final version of 1.7.0 will probably have all the extensions preloaded in the app locally instead of fetching things from extensions.turbowarp.org, but for now an unfiltered internet connection is required to use those extensions