[QA] Investigate module functionality

[sdzhepa]

There are no defined functional requirements for this module

TODO:

• review all module functional ability
• configure a couple of notification channel(emails, slack, telegram)
• create draft instruction on how to configure each channel
• quick smoke testing to get current QA status(functional bugs, Usability, Improvements )
• try to define requirements
• create instruction (at least as a draft )

Initial documentation from module author: https://github.com/magespecialist/notifier/wiki

[sdzhepa]

UPDATE:
During demo preparation were found several issue on the main/critical flow.

1. BLOCKER: Not possible to use Email notification channel. Exception and blank page #179
2. CRITICAL: Not possible to use the most part of predefined templates  #180
3. minor Title text is overlapped and not readable for Event Based Rule page #181
4. minor Title for button "New channel" should be fixed according to Magneto Naming Convention #182