fix(ecs-winston-format): fix types expression in ambient context error (#93)

- remove executable code in declaration file
- fix missing import error; Format is not exported from the winston root

Author: danielmwakanema

loggers/winston/index.d.ts

@@ -1,4 +1,4 @@
-import type { Format } from "winston";
+import type { Logform } from "winston";
 
 interface Config {
   /**
@@ -27,4 +27,6 @@ interface Config {
   apmIntegration?: boolean;
 }
 
-export = (opts?: Config) => Format
+declare function ecsFormat(opts?: Config): Logform.Format;
+
+export = ecsFormat;