webui: Tweak prettier setup

This should make us more consistent on formatting in local vs CI
diff --git a/webui/.prettierrc b/webui/.prettierrc
new file mode 100644
index 0000000..222861c
--- /dev/null
+++ b/webui/.prettierrc
@@ -0,0 +1,4 @@
+{
+  "tabWidth": 2,
+  "useTabs": false
+}