Most files suffered major changes

- Less ambiguous syntax
- Better parser (Chumsky only does tokenization now)
- Tidy(|ier) error handling
- Facade for simplified embedding
- External code grouped in (fairly) self-contained Systems
- Dynamic action dispatch
- Many STL additions

examples/hello-world/main.orc

@@ -1,3 +1,5 @@
-import std::io::print
-
-main := print "Hello, world!\n" "goodbye"
+const main := (
+  println "Hello, world!"
+    "success"
+)
+-- main := "Hello, World!\n"