Check testium version range (>= 0.2.0); add repository + LICENSE

The extension now probes '<serverPath> --version' on activation and refuses to
start (with a clear message) when testium is older than 0.2.0 — the release that
introduced 'testium lsp'. Unreadable version -> warn but proceed; binary not
found -> actionable error. Minimal component-wise comparator, no extra dep.

Also add the repository field and an EUPL-1.2 LICENSE file (Open VSX
prerequisites).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -6,6 +6,10 @@
   "publisher": "testium",
   "license": "EUPL-1.2",
   "icon": "icon.png",
+  "repository": {
+    "type": "git",
+    "url": "https://git.beafrancois.fr/v-and-v/testium_assist.git"
+  },
   "engines": {
     "vscode": "^1.80.0"
   },