automatically produce MSI files for releases

This commit:

- Adds config for building Windows installers
- Adds an action for fetching exe files built by goreleaser
- Adds an action for building Windows installers
- Adds an action for adding MSI files to an existing GH release
- Adds MSI signing to our release flow
- Disables homebrew formula bumping for prereleases
- Allows the release asset copying action to copy windows assets

.github/actions/build-msi/action.yml

@@ -0,0 +1,15 @@
+name: 'Build MSI'
+description: 'Build, sign, and release Windows installers using WiX'
+inputs:
+  version:
+    description: 'what version to use for the built MSI'
+    required: true
+  exe:
+    description: 'path to exe to wrap in MSI '
+    required: true
+outputs:
+  msi:
+    description: 'path to MSI file'
+runs:
+  using: 'node12'
+  main: 'dist/index.js'