Add a guide in the README

[XxX-Daniil-underscore-Zaikin-XxX]

• [x] Explain the VSCode build tasks
• [x] Summarize the papyrus lang VSCode thing
• [x] Summarize Spriggit
• [x] Summarize Caprica
• [x] Summarize GitHub Actions
• [x] Somehow summarize FOMODs
• [x] Add credits to Skyrim Scripting
• [x] Roughly explain the general workflow
• [x] Explain how to add script sources properly