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.
 
@@ -43,19 +43,19 @@ After cloning wherever you want the `duniter-v2s` repo with:
 git clone https://git.duniter.org/nodes/rust/duniter-v2s.git
 ```
 
-you can go to the root folder and build the substrate client with:
+you can go to the root folder and build the substrate client and default runtime with:
 
 ```bash
 cargo build
 ```
 
-This will take about **2 minutes** to download dependencies and **12 minutes** to build in debug mode. At this point, you only built the substrate client, a kind of "shell" in which lies the runtime. You can build the runtime and run a local blockchain with:
+This will take about **2 minutes** to download dependencies plus between 5 and **15 minutes** to build in debug mode depending on the power of your processor. At this point, you built the *substrate client* (a kind of "shell" in which lies the runtime) and the default *runtime* itself. You can run a local blockchain with:
 
 ```bash
-cargo run -- --dev --tmp
+cargo run -- --dev --tmp # here, --dev means --chain=dev which selects the gdev runtime
 ```
 
-Which should take about **1 minute**. When you see the logs, the blockchain is running and you can connect to it with polkadotjs app: [https://polkadot.js.org/apps/?rpc=ws://127.0.0.1:9944](https://polkadot.js.org/apps/?rpc=ws%3A%2F%2F127.0.0.1%3A9944). You should see blocks being added every 6 seconds. You can use Alice, Bob, etc test accounts to submit extrinsics.
+When you see the logs, the blockchain is running and you can connect to it with polkadotjs app: [https://polkadot.js.org/apps/?rpc=ws://127.0.0.1:9944](https://polkadot.js.org/apps/?rpc=ws%3A%2F%2F127.0.0.1%3A9944). You should see blocks being added every 6 seconds. You can use Alice, Bob, etc test accounts to submit extrinsics.
 
 ## Autocompletion
 
@@ -64,13 +64,13 @@ When using Duniter commands, you will benefit a lot from commands autocompletion
 ```bash
 # create local dir to store completion script
 mkdir -p ~/.local/share/duniter
-# build in release mode and export the bash completion file
-cargo run --release -- completion --generator bash > ~/.local/share/duniter/completion.bash
+# export the bash completion file
+cargo run -- completion --generator bash > ~/.local/share/duniter/completion.bash
 # add the following line to your ~/.bashrc to automatically load completion on startup
 [[ -f $HOME/.local/share/duniter/completion.bash ]] && source $HOME/.local/share/duniter/completion.bash
 ```
 
-Building in release mode for the first time is very long and can take up to **20 minutes**. You will then benefit from completion using `<Tab>` key and `*`.
+You will then benefit from completion using `<Tab>` key and `*`.
 
 ## End-to-end tests using cucumber
 
@@ -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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