Add beginner walkthrough documentation

docs/dev/beginner-walkthrough.md

 # Beginner walkthrough
 
-This is a beginner tutorial for those who do not have a previous experience with Rust ecosystem or need guidance to get familiar with Duniter v2s project. You'll need a development machine with an internet connection, at least **20 Go of free storage**, and **an hour or two** depending on your computing power.
+This is a beginner tutorial for those who do not have a previous experience with Rust ecosystem or need guidance to get familiar with Duniter v2s project. You'll need a development machine with an internet connection, at least **20 GB of free storage**, and **an hour or two** depending on your computing power.
 
 This walkthrough is based on the following video (french), don't hesitate to record an english voicecover if you feel so.
 
@@ -82,6 +82,6 @@ cargo cucumber
 
 which should take about **4 minutes** to build and run the tests. A highly detailed documentation about the end2end tests is available [in the dedicated folder](../../end2end-tests/README.md), you will learn how to read and modify the tests.
 
-## Get in tuch with us
+## Get in touch with us
 
 Wether you are stuck and need help or have sucessfully completed this tutorial, don't hesitate to get in touch with us on the Duniter forum! If you found this walkthrough useful, please 🙏 let us know on the [walkthrough topic](https://forum.duniter.org/t/contribuer-a-duniter-tutoriel-video/9770) on the forum 😊.
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