Add licenses plugin (#118)

source/plugins/licenses/queries/licenses.graphql

@@ -0,0 +1,20 @@
+query LicensesDefault {
+  licenses {
+    spdxId
+    name
+    nickname
+    key
+    limitations {
+      key
+      label
+    }
+    conditions {
+      key
+      label
+    }
+    permissions {
+      key
+      label
+    }
+  }
+}

source/plugins/licenses/queries/repository.graphql

@@ -0,0 +1,14 @@
+query LicensesRepository {
+  $account(login: "$owner") {
+    repository(name: "$name") {
+      licenseInfo {
+        spdxId
+        name
+        nickname
+        key
+      }
+      url
+      databaseId
+    }
+  }
+}