Notification improvements

[TTWNO]

• Add urgency field to Notification struct
• Add actions field to Notification struct
• Use itertools for chunking vector items by pairs (chunks not available in std::iter::Iterator yet)
• Default: Urgency::Normal
• No custom From<T> for Value or OwnedValue (all done through #[derive(...)])

[TTWNO]

Do not merge this yet. I still want to make certain structs PartialEq, Eq, etc.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 16.60%. Comparing base (efd02b7) to head (f49f940).
Report is 11 commits behind head on main.

Files	Patch %	Lines
odilia-notify/src/urgency.rs	0.00%	11 Missing ⚠️
odilia-notify/src/notification.rs	83.33%	3 Missing ⚠️
odilia-notify/src/action.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #135      +/-   ##
==========================================
+ Coverage   16.08%   16.60%   +0.51%     
==========================================
  Files          20       22       +2     
  Lines        1616     1650      +34     
==========================================
+ Hits          260      274      +14     
- Misses       1356     1376      +20     

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