[Epic] Conceptual rework & update

[cchexcode]

What I like

• Plan & Execute stages are separate
• Flexibility with handlebars placeholders and arguments
• Matrix builds
• Environment variable capturing in plan stage
• YAML and the flexibility with anchors
• The idea of local build environments using this tool

What I don't like

• Matrix builds dense vs. sparse needs some usability rework
• Deep nesting and complexity of the configuration file (although most of it is optional)
• GitHub workflow needs updating
• Code got messy af after adding that many features over time

What I want to add

• Some kind of optional TUI for visualising stages and and tasks
• Simplified command invocation just from the CLI, no config file needed
• Caching for commands based on a cache-key
• Architecture decision records
• Plugin system for additional flexibility

Things to investigate

• Potentially create a neomake based daemon / build server