0.10.0

Full Changelog

Adapting context ownership scheme from master branch of cpp.react

• BREAKING! context is no longer a thing that user should guarantee to die last
  after each ureact nodes using this context are destroyed.
  Instead, now it has shared pointer semantic and each ureact node has a copy of it.
  So context dies only after all its owners diy.
• BREAKING! count_ and lift_ are renamed to count_as and lift_as respectively.
• BREAKING! merge adaptor is no longer selecting result type based on the type of
  the first source event stream, but tries to determine result type using std::common_type.
  Additionally merge_as version is added to manually select the result type.
• BREAKING! equal_to is replaced with the opposite has_changed.
  All user overloads of equal_to are impacted.
• New adaptor monitor_change is added. It emits (old value, new value) pairs on
  monitored signal changes.
• New adaptor elements and its specializations keys and values are added.
  They do exactly the same that analogs from std::ranges do.
  https://en.cppreference.com/w/cpp/ranges/elements_view
• New adaptor stride is added.
  It does exactly the same that analog from std::ranges does.
  https://en.cppreference.com/w/cpp/ranges/stride_view
• New adaptor slice is added.
  ureact::slice(M, N) is equivalent to ureact::drop(M) | ureact::take(N - M).