[recipes] Explain how to run recipes uninstalled

[Matthias Clasen <matthiasc src gnome org>]

commit 2390a34c10318fcecfb4186f78380cac9031169b
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Apr 20 14:59:42 2017 -0400

    Explain how to run recipes uninstalled
    
    It is a convenient thing to do sometimes.

 README.md |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/README.md b/README.md
index 6c14930..e113487 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,12 @@ ninja -C build
 ninja -C build install
 ```
 
+Note that the install step is optional. Recipes works just fine uninstalled, like this:
+
+```
+GSETTINGS_SCHEMA_DIR=build/data ./build/src/gnome-recipes
+```
+
 jhbuild also knows how to build recipes.
 
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