v2.1.0

Changelog:

• Added selection modes to options
• Added selector union
• Added not-strictly-equal and not-loosely-equal operators for conditions
• Added pseudo-elements ::root, ::first, and ::last
• Added uniqueness filtering to options
• Added possibility to specify an appraisal function for options.collate
• Fixed a bug that caused read operations to fail on getter properties returning a new object on each access
• Fixed a bug that caused inherited properties to be ignored by wildcard selectors
• Deprecated the use of the empty selector in favor of ::root

Full Changelog: v2.0.0...v2.1.0