fix: fallback to <environment undetectable> in all environments

BREAKING CHANGE: `getUserAgent()` is no longer throwing an error if it cannot determine the user agent, it falls back to `<environment undetectable>` instead

src/browser.ts

@@ -2,6 +2,6 @@ export function getUserAgent(): string {
   try {
     return navigator.userAgent;
   } catch (e) {
-    return "<environment unknown>"
+    return "<environment undetectable>";
   }
 }

src/node.ts

@@ -10,6 +10,6 @@ export function getUserAgent(): string {
       return "Windows <version undetectable>";
     }
 
-    throw error;
+    return "<environment undetectable>";
   }
 }