doc: Add some build instructions to README

README.md

@@ -1,5 +1,4 @@
-About
-=====
+# About
 
 This is meant to be a more Linux packaging friendly copy of the AudioProcessing
 module from the [ WebRTC ](https://webrtc.googlesource.com/src) project. The
@@ -12,14 +11,32 @@ the code and hopefully eventually have a single point of packaging all the
 WebRTC code to help people reuse the code and avoid keeping private copies in
 several different projects.
 
-Feedback
-========
+# Building
+
+This project uses the [Meson build system](https://mesonbuild.com/). The
+quickest way to build is:
+
+```sh
+# Initialise into the build/ directory, for a prefixed install into the
+# install/ directory
+meson . build -Dprefix=$PWD/install
+
+# Run the actual build
+ninja -C build
+
+# Install locally
+ninja -C build install
+
+# The libraries, headers, and pkg-config files are now in the install/
+# directory
+```
+
+# Feedback
 
 Patches, suggestions welcome. You can file an issue on our Gitlab
 [repository](https://gitlab.freedesktop.org/pulseaudio/webrtc-audio-processing/).
 
-Notes
-====
+# Notes
 
 1. It might be nice to try LTO on the library. We build a lot of code as part
    of the main AudioProcessing module deps, and it's possible that this could