Add HelloPy and HelloRust. Rust support not functional yet.

Author: erlingrj

defaults/HelloPy.lf

@@ -0,0 +1,8 @@
+target Python;
+
+main reactor {
+    reaction (startup)  {=
+        print("Hello World!")
+    =}
+} 
+

defaults/HelloRust.lf

@@ -0,0 +1,8 @@
+target Rust;
+
+main reactor {
+    reaction (startup)  {=
+        println!("Hello World!");
+    =}
+} 
+

src/package/mod.rs

@@ -216,8 +216,9 @@ impl ConfigFile {
         let hello_world_code: &'static str = match self.apps[0].target {
             TargetLanguage::Cpp => include_str!("../../defaults/HelloCpp.lf"),
             TargetLanguage::C => include_str!("../../defaults/HelloC.lf"),
+            TargetLanguage::Python => include_str!("../../defaults/HelloPy.lf"),
             TargetLanguage::TypeScript => include_str!("../../defaults/HelloTS.lf"),
-            _ => panic!("Target langauge not supported yet"), // FIXME: Add examples for other programs
+            _ => panic!("Target langauge not supported yet"), //FIXME: Add support for Rust.
         };
 
         write(Path::new("./src/Main.lf"), hello_world_code)?;