[gtksourceview] Adwaita.xml: tweak styling for Meson

[Christian Hergert <chergert src gnome org>]

commit 521dbb2d1656d388441defa0b658034dda0ef787
Author: Christian Hergert <chergert redhat com>
Date:   Thu Dec 30 11:50:52 2021 -0800

    Adwaita.xml: tweak styling for Meson

 data/styles/Adwaita.xml | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/data/styles/Adwaita.xml b/data/styles/Adwaita.xml
index 138bd14a..2e54c47a 100644
--- a/data/styles/Adwaita.xml
+++ b/data/styles/Adwaita.xml
@@ -151,6 +151,10 @@
   <style name="xml:attribute-name"          foreground="pink1"/>
   <style name="xml:attribute-value"         foreground="text4"/>
 
+  <style name="meson:builtin-command"       foreground="teal" bold="true"/>
+  <style name="meson:string"                foreground="pink1"/>
+  <style name="meson:operator"              foreground="text5" bold="true"/>
+
   <style name="def:base-n-integer"          foreground="numbers"/>
   <style name="def:builtin"                 bold="true"/>
   <style name="def:boolean"                 foreground="numbers"/>