Add option to sanitise texts in HTML format

HTML format requires that `<`, `>`, etc. have to be replaced with `<`, `>`, etc. Add an option to do that.

Currently, if you add, say, a `<` in your commit (which is configured to be sent as a message), it will fail to send the message.

The issue concerns the GitHub Action's Telegram message handling when HTML formatting is selected, with commit messages containing < characters as the reproduction. Start by locating the action entry point and its message-format handling, then verify that an option escapes HTML-sensitive characters before sending. Done means the option works for commit messages containing < and > without send failures.

Written by the indexing model from the issue text.