Bark - add critical level alert plus ?volume= argument

[pb8DvwQkfRR]

Description:

Critical Alert will ignore silent and Do Not Disturb modes.
Volume range: 0-10.

Finb/Bark@f059fde

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/pb8DvwQkfRR/apprise.git@bark-critical

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  bark://api.day.app/<device_key>/?level=critical&volume=1

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 99.35%. Comparing base (f37dfbf) to head (c33984c).

Files with missing lines	Patch %	Lines
apprise/plugins/bark.py	80.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1239      +/-   ##
==========================================
- Coverage   99.36%   99.35%   -0.02%     
==========================================
  Files         147      147              
  Lines       20555    20570      +15     
  Branches     3663     3668       +5     
==========================================
+ Hits        20425    20437      +12     
- Misses        121      122       +1     
- Partials        9       11       +2     

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