feat: restructure k-launcher workspace and add core functionality

- Updated Cargo.toml to include a new k-launcher crate and reorganized workspace members.
- Introduced a README.md file detailing the project philosophy, architecture, and technical specifications.
- Implemented a new Kernel struct in k-launcher-kernel for managing plugins and search functionality.
- Created a Plugin trait for plugins to implement, allowing for asynchronous search operations.
- Developed k-launcher-ui with an Iced-based UI for user interaction, including search input and result display.
- Added AppsPlugin and CalcPlugin to handle application launching and basic calculations, respectively.
- Established a theme module for UI styling, focusing on an Aero aesthetic.
- Removed unnecessary main.rs files from plugin crates, streamlining the project structure.

crates/k-launcher-kernel/Cargo.toml

@@ -4,3 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+async-trait = { workspace = true }
+futures = { workspace = true }
+serde = { workspace = true }
+tokio = { workspace = true }