[gedit-plugins] Update build instruccions

[Jordi Mas <jmas src gnome org>]

commit 86b147eee3dd4305e18bc2eba94522942bb3527e
Author: Jordi Mas <jmas softcatala org>
Date:   Thu May 30 09:30:09 2019 +0200

    Update build instruccions

 README | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/README b/README
index aa63cee..3503668 100644
--- a/README
+++ b/README
@@ -7,6 +7,8 @@ for gedit.
 Installation
 ============
 
-For the moment, you have to ./configure with --prefix=same prefix as you
-configured gedit with.
+To install follow these steps:
 
+cd build-aux
+meson
+sudo ninja install