fix(54): pipe observable to signal

[tarashevchuk0401]

Checklist for challenge submission

• Start your PR message with Answer:${challenge_number}

Warning:

• If you want feedback or review, you must support the project on GitHub:
  • $5 per review
  • $25 for lifetime reviews
  • Create one of more challenges
  • Have many valuable contributions to the project

Alternatively, you can still submit your PR to join the list of answered challenges or to be reviewed by a community member. 🔥