doc: Fix micromamba development environment creation command (#141)

* doc: Fix micromamba development environment creation command

Signed-off-by: Maharshi Basu <basumaharshi10@gmail.com>

* doc: Update instruction for wasm and non-wasm builds

Signed-off-by: Maharshi Basu <basumaharshi10@gmail.com>

---------

Signed-off-by: Maharshi Basu <basumaharshi10@gmail.com>

Author: MashyBasker

CONTRIBUTING.md

@@ -31,7 +31,7 @@ or miniconda installed cd into the xeus-cpp directory and set setup your environ
 
 ```bash
 cd xeus-cpp
-micromamba create -n xeus-cpp environment-dev.yml
+micromamba create -f environment-dev.yml -y
 micromamba activate xeus-cpp
 ```
 
@@ -56,4 +56,4 @@ and the python tests by executing
 ```bash
 cd ../../test
 pytest -sv test_xcpp_kernel.py
-```
+```