Feature: Notifications flow diagrams recreation

[TomerPacific]

Summary

This PR recreates the following three diagrams using draw.io

1. Desktop Notification Flow Chart
2. Email Notification Flow Chart
3. Push Notification Flow Chart

All files are in a draw.io format and have been placed inside the images directory with an equivalent name to the same flow chart in .png format.

Ticket Link

Resolves #7348

[mattermost-build]

Hello @TomerPacific,

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[cwarnermm]

Thanks, @TomerPacific!

[github-actions]

Newest code from TomerPacific has been published to preview environment for Git SHA 8280093

[Rutam21]

@lindy65 I would like to do the QA testing for this PR. Please assign this to me. Thanks.

[Rutam21]

The changes in this PR have been verified and they strictly follow the guidelines mentioned in the original ticket.

Here's a summary of the observed outcomes through this PR.

• Mattermost desktop notification flow chart XML has been added with a .drawio extension.
• Mattermost email notification flow chart XML has been added with a .drawio extension.
• Mattermost desktop notification flow chart XML has been added with a .drawio extension.
• All these XML files have been added in the /images folder as advised in the original ticket.
• All these XML files bear the same name as the existing PNG flow diagram files.
• The colors/fonts/text and general appearance are similar to the current flow diagram published in the product documentation.
• The XML files for these flow charts can be opened and edited further using Draw IO as instructed in the original ticket.

I've attached a video as a confirmation, comparing the existing flow diagrams and the newly created flow charts, and have also tried editing it successfully.

PR-7470.QA.Testing.mp4

cc: @lindy65