[Fix] Watchdog: escape subject and body for webhooks

[mrclschstr]

Proposal for escaping subject and body for webhooks, which fixes #5760. I tried to use a generic approach as mentioned here:

As Ben Blank said, there are only three characters that need to be escaped in the replacement string (escapes themselves, forward slash for end of statement and & for replace all)

IP ban notifications using Pushover are now working for me:

[milkmaker]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[mrclschstr]

Bump, still relevant