readme: Modernize build and installation instruction

.gitignore

@@ -1,4 +1,4 @@
-build*
+build*/
 Xcode/*
 *~
 *.pyc

README.md

@@ -69,6 +69,20 @@ One can observe that GJK-based approaches largely outperform solutions based on
 - [Jiminy](https://github.com/duburcqa/jiminy) A simulator based on Pinocchio.
 - [ocs2](https://github.com/leggedrobotics/ocs2) A toolbox for Optimal Control for Switched Systems (OCS2)
 
+## Installation
+
+### Conda
+
+Coal can be installed from the [conda-forge channel](https://anaconda.org/conda-forge/coal):
+
+```bash
+conda install coal -c conda-forge
+```
+
+## Build
+
+You can find build instruction [here](./development/build.md).
+
 ## C++ example
 Both the C++ library and the python bindings can be installed as simply as `conda -c conda-forge install coal`.
 The `.so` library, include files and python bindings will then be installed under `$CONDA_PREFIX/lib`, `$CONDA_PREFIX/include` and `$CONDA_PREFIX/lib/python3.XX/site-packages`.

development/build.md

@@ -0,0 +1,17 @@
+# Build and install from source with Pixi
+
+To build Coal from source the easiest way is to use [Pixi](https://pixi.sh/latest/#installation).
+
+[Pixi](https://pixi.sh/latest/) is a cross-platform package management tool for developers that
+will install all required dependencies in `.pixi` directory.
+It's used by our CI agent so you have the guarantee to get the right dependencies.
+
+Run the following command to install dependencies, configure, build and test the project:
+
+```bash
+pixi run test
+```
+
+The project will be built in the `build` directory.
+You can run `pixi shell` and build the project with `cmake` and `ninja` manually.
+