Add multilingual Agila learning examples and Git practice guide

tl/flying-v-validation-and-capstone/main.fv

@@ -0,0 +1,12 @@
+import agila
+
+fn main() {
+    mesh := agila.MeshDescriptor{
+        vertex_count: 3
+        index_count: 3
+    }
+    agila.submit_mesh(mesh) or {
+        eprintln(err.msg())
+        return
+    }
+}