client/web: add Inter font

Adds Inter font and uses it as the default for the web UI.
Creates a new /assets folder to house the /fonts, and moves /icons
to live here too.

Updates #10261

Signed-off-by: Sonia Appasamy <sonia@tailscale.com>

client/web/tailwind.config.js

@@ -5,6 +5,31 @@ module.exports = {
     "./src/**/*.{js,ts,jsx,tsx}",
   ],
   theme: {
+    fontFamily: {
+      sans: [
+        "Inter",
+        "-apple-system",
+        "BlinkMacSystemFont",
+        "Helvetica",
+        "Arial",
+        "sans-serif",
+      ],
+      mono: [
+        "SFMono-Regular",
+        "SFMono Regular",
+        "Consolas",
+        "Liberation Mono",
+        "Menlo",
+        "Courier",
+        "monospace",
+      ],
+    },
+    fontWeight: {
+      normal: "400",
+      medium: "500",
+      semibold: "600",
+      bold: "700",
+    },
     extend: {},
   },
   plugins: [],