Update dependency jekyll-feed to ~> 0.15.0

This MR contains the following updates:

Package	Update	Change
jekyll-feed	minor	~> 0.12.0 -> ~> 0.15.0

---

Renovate configuration

📅 Schedule: At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by WhiteSource Renovate. View repository job log here.