Add `declare` to checker interfaces to prevent property renaming

Change-Id: Ie7aae07bc330389e3aff76cd4a3b88b5ad2caae2

web/types.ts

diff --git a/web/types.ts b/web/types.ts
index 772ad5d..ed7c31f 100644
--- a/web/types.ts
+++ b/web/types.ts
@@ -15,7 +15,8 @@
  * limitations under the License.
  */
 
-export interface Check {
+/** `declare` is required for preventing property renaming. */
+export declare interface Check {
   state: string;
   checker_name: string;
   checker_description: string;
@@ -26,7 +27,8 @@
   finished?: number;
 }
 
-export interface Checker {
+/** `declare` is required for preventing property renaming. */
+export declare interface Checker {
   repository?: string;
   blocking?: string[];
   query?: string;