Notifiarr footer and icon attributes set

[caronc]

Description:

Related issue (if applicable): #949 and #953

Added footer and image details as part of the notifiarr payload

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in as follows:
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@949-notifiarr-extra-requests

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  "notifiarr://credentials"

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

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Files	Coverage Δ
apprise/plugins/NotifyNotifiarr.py	100.00% <100.00%> (ø)

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