isokit: engine core, theme and Rhai scene runtime with prefab library

crates/isokit-core/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "isokit-core"
+description = "Isometric scene engine: projection, primitives, sprites, depth sort, SVG output"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+serde = { workspace = true }