Add Ubuntu font

assets/stylesheets/global/_variables-dark.scss

@@ -1,4 +1,4 @@
-$baseFont: -apple-system, BlinkMacSystemFont, San Francisco, Segoe UI, Roboto, Helvetica Neue, Helvetica, Arial, sans-serif;
+$baseFont: -apple-system, BlinkMacSystemFont, 'San Francisco', 'Segoe UI', Roboto, Ubuntu, 'Helvetica Neue', Arial, sans-serif;
 $monoFont: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, Courier, monospace;
 $boldFontWeight: 500;
 $bolderFontWeight: 600;

assets/stylesheets/global/_variables.scss

@@ -1,4 +1,4 @@
-$baseFont: -apple-system, BlinkMacSystemFont, San Francisco, Segoe UI, Roboto, Helvetica Neue, Helvetica, Arial, sans-serif;
+$baseFont: -apple-system, BlinkMacSystemFont, 'San Francisco', 'Segoe UI', Roboto, Ubuntu, 'Helvetica Neue', Arial, sans-serif;
 $monoFont: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, Courier, monospace;
 $boldFontWeight: 500;
 $bolderFontWeight: 600;