fix: allow ":" character in digestAuth password (#532)

`str.split()` -function would cut rest of the password off when
encountering a "`:`" character.


Old:
```javascript
let s = 'user:passwordwith:character';
const [user, pass] = userpass.split(':');
console.log(`User '${user}' and pass '${pass}'`);
``` 
Output: `User 'user' and pass 'passwordwith'`

Fixed:
```javascript
const user = userpass.split(':', 1);
const pass = userpass.slice(user[0].length+1);
console.log(`User '${user}' and pass '${pass}'
``` 
Output: `User 'user' and pass 'passwordwith:character'`

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit


- **Bug Fixes**
- Improved the extraction process for username and password from the
userpass string, enhancing clarity and maintainability.

- **Refactor**
- Refined the logic within the digest authentication header function for
better readability without altering its overall functionality.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

src/utils.ts

@@ -98,7 +98,9 @@ export function digestAuthHeader(method: string, uri: string, wwwAuthenticate: s
   }
 
   let qop = opts.qop || '';
-  const [ user, pass ] = userpass.split(':');
+  const index = userpass.indexOf(':');
+  const user = userpass.substring(0, index);
+  const pass = userpass.substring(index + 1);
 
   let nc = String(++NC);
   nc = `${NC_PAD.substring(nc.length)}${nc}`;