Add multilingual Agila learning examples and Git practice guide

en/ada-functions-and-packages/README.md

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+# A reusable study-plan calculation
+
+Build and test a small lesson-count component. Start with the nested function; optionally extract it into an Ada package in a local multi-file project.
+
+- State the Total/Done policy without referring to source code.
+- Check (0,0), (4,0), (4,3), (4,4), and (4,5).
+- Explain why the subtraction is reached only when Done is below Total.
+- Keep calculation separate from output.
+- Include a review note explaining one design choice and one limitation.

en/ada-functions-and-packages/main.adb

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+with Ada.Text_IO;
+
+procedure Main is
+   function Remaining (Total, Done : Natural) return Natural is
+   begin
+      if Done >= Total then
+         return 0;
+      end if;
+      return Total - Done;
+   end Remaining;
+begin
+   Ada.Text_IO.Put_Line (Natural'Image (Remaining (4, 1)));
+end Main;