add link to the old code branch

Author: Zer0-bit

README.md

@@ -9,10 +9,14 @@
 ---
 ### Gaggiuino started as an idea to improve an already capable coffee machine while keeping the machine appearance and button functionality as close as possible to the original.
 ---
-### For install instructions head to the project [documentation](https://gaggiuino.github.io/#/) section.
+
+### For install instructions head to the project [Documentation](https://gaggiuino.github.io/#/) section.
 
 ### For install or upgrade binaries head over to [Releases](https://github.com/Zer0-bit/gaggiuino/releases).
 
-### For project related help join us on [discord](https://discord.gg/gaggiuino).
+### For project related help join us on [Discord](https://discord.gg/gaggiuino).
+
+---
+##### The legacy version of the project can be found by switching branch or alternatively [click here](https://github.com/Zer0-bit/gaggiuino/tree/release/stm32-blackpill).
 
-</div>
+</div>