fix incorrect typings for TracerOptions interface

types/dd-trace/dd-trace-tests.ts

@@ -9,6 +9,7 @@ tracer.init({
         debug: msg => {},
         error: err => {},
     },
+    tags: { tracerEnv: 'dev'}
 });
 
 function useWebFrameworkPlugin(plugin: "express" | "hapi" | "koa" | "restify") {

types/dd-trace/index.d.ts

@@ -110,6 +110,11 @@ interface TracerOptions {
         debug: (message: string) => void;
         error: (err: Error) => void;
     };
+
+    /**
+     * Global tags that should be assigned to every span.
+     */
+    tags?: { [key: string]: any };
 }
 
 interface ExperimentalOptions {}