Added instrumentModule function definition into index.d.ts

src/index.d.ts

@@ -40,6 +40,15 @@ declare module '@thundra/core' {
    */
   export function tracer(): ThundraTracer;
 
+  /**
+   * Instruments given module if it is supported
+   * @param moduleName {string} name of the module to be instrumented
+   * @param module the module to be instrumented
+   * @return {boolean} {@code true} if the given has been instrumented,
+   *                   {@code false} otherwise
+   */
+  export function instrumentModule(moduleName: string, module: any): boolean;
+
   /**
    * Sets the tag
    * @param {string} name the tag name