comcast.net email template added

[caronc]

Description:

Related issue (if applicable): #1058

comcast.net email template added. Users of comcast can format their email using apprise as:

• mailto://user:pass@comcast.net

Checklist

• [x] The code change is tested and works locally.
• [x] There is no commented out code in this PR.
• [x] No lint errors (use flake8)
• [x] 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@1058-comcast-email-template

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  "mailto://user:pass@comcast.net"

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (31a4f2e) 99.27% compared to head (6998f99) 99.27%. Report is 1 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1059 +/- ## ======================================= Coverage 99.27% 99.27% ======================================= Files 135 135 Lines 17600 17603 +3 Branches 3592 3593 +1 ======================================= + Hits 17472 17475 +3 Misses 119 119 Partials 9 9 ```

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[caronc]

Based configuration off of official documentation .