Add AppCast Jekyll Folder for building appcasts

[MattKiazyk]

Description

This adds an AppCast folder that includes the code needed for a manual release process.

1. On a "release" (Preview release or regular) the Jekyll website will get recreated
2. Will loop through releases, searching for a sparkle:edSignature= comment on the release
3. Will create appcast.xml and appcast_pre.xml based on those releases.

Note: All zip's/dmg will need be included in the release. This includes the proper signing and notarizing needed by Sparkle.

The preface to making sure this works as it should is to get artifacts building properly which currently they are not.

Related Issue

• ✨ CodeEdit App Updater #644

Checklist

• I read and understood the contributing guide as well as the code of conduct
• My changes generate no new warnings
• My code builds and runs on my machine
• I documented my code
• Review requested

Screenshots

[austincondiff]

Looks great, very nice! ✅