Added Feishu Custom Bot Support

Description:

Related issue (if applicable): n/a

Added Feishu Custom Bot support

Source: https://open.feishu.cn/
Icon Support: No
Message Format: Text
Message Limit: 19985 Characters per message

Account Setup

Register your account with Feishu and then follow these instructions to create a custom bot (and acquire the token you need).

Syntax

Valid syntax is as follows:

feishu://{token}

Parameter Breakdown

Variable	Required	Description
token	Yes	The token you generated as part of your Fieshu Custom Bot Creation (via your account)

New Service Completion Status

[x] apprise/plugins/NotifyFeishu.py
[x] KEYWORDS
- add new service into this file (alphabetically).
[x] README.md
- add entry for new service to table (as a quick reference)
[x] packaging/redhat/python-apprise.spec
- add new service into the %global common_description

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@feishu-bot-support

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

Codecov Report

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

Project coverage is 99.27%. Comparing base (f461b68) to head (0ebe87a). Report is 1 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1099 +/- ## ======================================= Coverage 99.27% 99.27% ======================================= Files 138 139 +1 Lines 17963 18019 +56 Branches 3670 3676 +6 ======================================= + Hits 17833 17889 +56 Misses 121 121 Partials 9 9 ```

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caronc / apprise