SHA256 Config Generator and CSS/Doc Improvements

[caronc]

Description:

Related issue (if applicable): refs #102

This is just a small PR with various changes:

• clean up some documentation - provided examples for curl from the API website
• dark mode improvements
• Added new configuration generator based on sha256 strings to allow people to generate more obfuscated configurations that can be exposed to the internet easier without being guessed.
• default configuration remains at apprise, but added a global variable APPRISE_DEFAULT_CONFIG_ID can be specified to over-ride this value if one wants.

[codecov-commenter]

Codecov Report

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

Comparison is base (46d9533) 95.16% compared to head (c27bc31) 95.23%. Report is 2 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #151 +/- ## ========================================== + Coverage 95.16% 95.23% +0.07% ========================================== Files 7 7 Lines 703 714 +11 ========================================== + Hits 669 680 +11 Misses 34 34 ```

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