Add Toast documentation and implement close button customization features.

[terabytesoftw]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.65%. Comparing base (450f170) to head (5fcd52c).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #283   +/-   ##
=========================================
  Coverage     99.65%   99.65%           
- Complexity      689      695    +6     
=========================================
  Files            23       23           
  Lines          2909     2927   +18     
=========================================
+ Hits           2899     2917   +18     
  Misses           10       10           

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