Use system font stack (#1326)

Closes https://github.com/woodpecker-ci/woodpecker/issues/1316

Applied suggestion by @silverwind

web/src/App.vue

@@ -54,7 +54,6 @@ export default defineComponent({
 
 <style scoped>
 .app {
-  font-family: Avenir, Helvetica, Arial, sans-serif;
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
 }

web/windi.config.ts

@@ -22,6 +22,17 @@ export default defineConfig({
       },
       stroke: (theme) => theme('colors'),
       fill: (theme) => theme('colors'),
+      fontFamily: [
+        'system-ui',
+        '-apple-system',
+        'Segoe UI',
+        'Roboto',
+        'Helvetica Neue',
+        'Noto Sans',
+        'Liberation Sans',
+        'Arial',
+        'sans-serif',
+      ],
     },
   },
   plugins: [typography],