add regex to Notifier

[Rommmmaha]

Describe the feature

Add regex filtering for player nicknames in join/leave notifications.

Use Cases:

• Notify about specific players joining or leaving.
• Filter out notifications for unwanted players.
• Personal reason: I would like to filter out bots because they spam my chat when I am near them.

Potential Implementation Issues:

Remove formatting codes before running regex. (This is mentioned because formatting is not cleared when writing a nickname to the chat.)

Design Example:

A single input field named "Regex filter" with a default value of ^.+$.

Before submitting a suggestion

• [x] This feature doesn't already exist in the client. (I have checked every module and their settings on the latest dev build)

• [x] This wasn't already suggested. (I have searched suggestions on GitHub and read the FAQ)