Add custom font-family (#117)

assets/css/main.scss

@@ -0,0 +1,10 @@
+---
+# Only the main Sass file needs front matter (the dashes are enough)
+search: false
+---
+
+@charset "utf-8";
+
+$sans-serif: -apple-system, BlinkMacSystemFont, "Roboto", "Segoe UI", "Noto Sans", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
+@import "minimal-mistakes/skins/{{ site.minimal_mistakes_skin | default: 'default' }}"; // skin
+@import "minimal-mistakes"; // main partials