DeckCraft guides

1. 01How to install DeckCraft on macOS, Windows and LinuxWhich DeckCraft 0.5.0 file to download for your OS and CPU, how to verify it, and how to build DeckCraft from source. Based on the official README and the v0.5.0 release.
2. 02DeckCraft: a free, open-source Microsoft PowerPoint alternativeWhat DeckCraft 0.5.0 is, what it already does, and where it still falls short of Microsoft PowerPoint. Based only on the official DeckCraft README and docs.