[gtksourceview] solarized: add styling for diffs

[Christian Hergert <chergert src gnome org>]

commit 1e14c456d2002e48169dfe32a247601bd72c923b
Author: Christian Hergert <chergert redhat com>
Date:   Mon May 2 13:53:45 2022 -0700

    solarized: add styling for diffs
    
    This makes things look somewhat similar to Solarized patch viewing in
    other editors.
    
    The change-line is kept yellow instead of orange since that isn't really
    used for display anywhere notable, yet can be used by IDE tooling for
    the gutters and orange is too close to red there.

 data/styles/solarized-dark.xml  | 7 +++++++
 data/styles/solarized-light.xml | 7 +++++++
 2 files changed, 14 insertions(+)
---
diff --git a/data/styles/solarized-dark.xml b/data/styles/solarized-dark.xml
index 30754aa9..938a62b1 100644
--- a/data/styles/solarized-dark.xml
+++ b/data/styles/solarized-dark.xml
@@ -108,6 +108,13 @@
   <style name="def:preformatted-section"    foreground="blue"/>
   <style name="def:list-marker"             foreground="orange"/>
 
+  <!-- Diff -->
+  <style name="diff:added-line"             foreground="green"/>
+  <style name="diff:removed-line"           foreground="red"/>
+  <style name="diff:changed-line"           foreground="yellow"/>
+  <style name="diff:location"               foreground="blue"/>
+  <style name="diff:diff-file"              foreground="yellow"/>
+
   <!-- Operators -->
   <style name="def:operator"                foreground="green"/>
 
diff --git a/data/styles/solarized-light.xml b/data/styles/solarized-light.xml
index 448caa75..66e60ccf 100644
--- a/data/styles/solarized-light.xml
+++ b/data/styles/solarized-light.xml
@@ -109,6 +109,13 @@
   <style name="def:preformatted-section"    foreground="blue"/>
   <style name="def:list-marker"             foreground="orange"/>
 
+  <!-- Diff -->
+  <style name="diff:added-line"             foreground="green"/>
+  <style name="diff:removed-line"           foreground="red"/>
+  <style name="diff:changed-line"           foreground="yellow"/>
+  <style name="diff:location"               foreground="blue"/>
+  <style name="diff:diff-file"              foreground="yellow"/>
+
   <!-- Operators -->
   <style name="def:operator"                foreground="green"/>