Add public/data to .eslintignore in desktop-client (#1199)

This fixes an error that you’ll see about an unused export if you build
before linting.

packages/desktop-client/.eslintignore

 bundle.browser.js
 build/
 public/kcab/
+public/data/
 **/node_modules/*
-node_modules/
\ No newline at end of file
+node_modules/

upcoming-release-notes/1199.md

+---
+category: Maintenance
+authors: [j-f1]
+---
+
+Add `public/data` to `.eslintignore` in `desktop-client`