Add Fastlane config and update release workflow for v2

Single unified "Yattee" scheme replaces per-platform schemes.
Release workflow now has toggleable platform inputs instead of
matrix strategy. Standalone mac notarized workflow removed in
favor of the build_mac_notarized toggle. Share extension bundle
ID updated from Open-in-Yattee to ShareExtension.

fastlane/README.md

@@ -0,0 +1,85 @@
+fastlane documentation
+----
+
+# Installation
+
+Make sure you have the latest version of the Xcode command line tools installed:
+
+```sh
+xcode-select --install
+```
+
+For _fastlane_ installation instructions, see [Installing _fastlane_](https://docs.fastlane.tools/#installing-fastlane)
+
+# Available Actions
+
+### bump_build
+
+```sh
+[bundle exec] fastlane bump_build
+```
+
+Bump build number and commit
+
+### bump_version
+
+```sh
+[bundle exec] fastlane bump_version
+```
+
+Bump version number and commit
+
+----
+
+
+## iOS
+
+### ios beta
+
+```sh
+[bundle exec] fastlane ios beta
+```
+
+Push a new beta build to TestFlight
+
+----
+
+
+## tvos
+
+### tvos beta
+
+```sh
+[bundle exec] fastlane tvos beta
+```
+
+Push a new beta build to TestFlight
+
+----
+
+
+## Mac
+
+### mac beta
+
+```sh
+[bundle exec] fastlane mac beta
+```
+
+Push a new beta build to TestFlight
+
+### mac build_and_notarize
+
+```sh
+[bundle exec] fastlane mac build_and_notarize
+```
+
+Build for Developer ID distribution and notarize
+
+----
+
+This README.md is auto-generated and will be re-generated every time [_fastlane_](https://fastlane.tools) is run.
+
+More information about _fastlane_ can be found on [fastlane.tools](https://fastlane.tools).
+
+The documentation of _fastlane_ can be found on [docs.fastlane.tools](https://docs.fastlane.tools).