add plugin marketplace manifest

Lets users run /plugin marketplace add only-cli/oc and install the
existing skill as a plugin, alongside the skills.sh and manual-copy
distribution paths.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -0,0 +1,14 @@
+{
+  "name": "only-cli",
+  "owner": { "name": "only-cli" },
+  "plugins": [
+    {
+      "name": "only-cli",
+      "source": { "source": "github", "repo": "only-cli/oc" },
+      "description": "Browse websites from the terminal in a few hundred tokens",
+      "version": "0.2.0",
+      "homepage": "https://github.com/only-cli/oc",
+      "license": "MIT"
+    }
+  ]
+}

.claude-plugin/plugin.json

@@ -0,0 +1,5 @@
+{
+  "name": "only-cli",
+  "description": "Browse websites from the terminal in a few hundred tokens",
+  "version": "0.2.0"
+}