feat: add displayLang test (#5495)

* feat(e2e): add language extension to setup

This adds a slimmed-down version of the Spanish Language Pack and also
adds a `languagepacks.json` to the e2e `workspaceDir` which allows use
to run a test suite passing the `--locale es` flags to simulate a
different display language.

* feat: add e2e test for display language patch

This tests loading code-server in Spanish using the `--locale` flag.

* fixup!: use JSON.stringify for readability

* fixup!: add comment about langaugepacks temp fix

* fixup!: slim down translations

* fixup!: slim down package.json for lang. ext

test/e2e/displayLang.test.ts

@@ -0,0 +1,14 @@
+import * as path from "path"
+import { describe, test, expect } from "./baseFixture"
+
+// Given a code-server environment with Spanish Language Pack extension installed
+// and a languagepacks.json in the data-dir
+describe("--locale es", ["--extensions-dir", path.join(__dirname, "./extensions"), "--locale", "es"], {}, () => {
+  test("should load code-server in Spanish", async ({ codeServerPage }) => {
+    // When
+    const visible = await codeServerPage.page.isVisible("text=Explorador")
+
+    // Then
+    expect(visible).toBe(true)
+  })
+})