fix: replace URL.canParse()

[URL.canParse][1] was only pretty recently created, and is not
available in many environments.

We can instead wrap a `URL` creation in a `try..catch`, as listed in
MDN. Unfortunately, this is a bit slower, but at least it works almost
everywhere.

[1]: https://developer.mozilla.org/en-US/docs/Web/API/URL/canParse_static

Fixes: braintree#78

src/index.ts

@@ -21,7 +21,13 @@ function decodeHtmlCharacters(str: string) {
 }
 
 function isValidUrl(url: string): boolean {
-  return URL.canParse(url);
+  try {
+    // We can replace this with URL.canParse() once it's more widely available
+    new URL(url); // eslint-disable-line no-new -- We're only checking for exceptions
+    return true;
+  } catch (error) {
+    return false;
+  }
 }
 
 function decodeURI(uri: string): string {