Pango Markup: Use double quotes for gettext

https://gitlab.gnome.org/jwestman/blueprint-compiler/-/commit/aa13c8f5af137bbedd1781d903e923d45d7c41fb

Author: sonnyp

src/Pango Markup/main.blp

@@ -11,32 +11,32 @@ Adw.StatusPage {
     spacing: 12;
 
     Label label {
-      label: _('<span foreground="blue" size="x-large">Blue text</span> is <i>cool</i>!');
+      label: _("<span foreground='blue' size='x-large'>Blue text</span> is <i>cool</i>!");
       use-markup: true;
     }
 
     Label label2 {
-      label: _('<i>Italic text</i> and <b>Bold text</b>');
+      label: _("<i>Italic text</i> and <b>Bold text</b>");
       use-markup: true;
     }
 
     Label label3 {
-      label: _('<s>Strikethrough text</s> and <u>Underlined text</u>');
+      label: _("<s>Strikethrough text</s> and <u>Underlined text</u>");
       use-markup: true;
     }
 
     Label label4 {
-      label: _('<span font_family="Monospace" weight="bold" size="large">Monospace Bold Large</span>');
+      label: _("<span font_family='Monospace' weight='bold' size='large'>Monospace Bold Large</span>");
       use-markup: true;
     }
 
     Label label5 {
-      label: _('<span strikethrough="true" strikethrough_color="red">Strikethrough Red</span> and <span underline="double" underline_color="green">Double Underline Green</span>');
+      label: _("<span strikethrough='true' strikethrough_color='red'>Strikethrough Red</span> and <span underline='double' underline_color='green'>Double Underline Green</span>");
       use-markup: true;
     }
 
     Label label6 {
-      label: _('<span background="red" text_transform="uppercase" line_height="1.5">Background Red, Uppercase, Line Height 1.5</span>');
+      label: _("<span background='red' text_transform='uppercase' line_height='1.5'>Background Red, Uppercase, Line Height 1.5</span>");
       use-markup: true;
     }