Add multilingual Agila learning examples and Git practice guide

en/flying-v-ui-contracts/main.fv

@@ -0,0 +1,11 @@
+import agila
+
+fn main() {
+    view := agila.Column{
+        children: [
+            agila.Text{value: 'Today: understand one function'},
+            agila.Button{label: 'Begin practice'},
+        ]
+    }
+    agila.preview(view)
+}