Prepare for v0.27.4

[hoc081098]

0.27.4 (2022-05-27)

Bug fixes

• withLatestFrom should iterate over Iterable<Stream>s only once when the stream is listened to.
• Fix analyzer warnings when using Dart 2.16.0.

Features

• Add mapNotNull/MapNotNullStreamTransformer.
• Add whereNotNull/WhereNotNullStreamTransformer.

Documentation

• Fix grammar errors in code examples (thanks to @fzyzcjy).
• Update rxmarbles URL for RaceStream (thanks to @Péter Ferenc Gyarmati).

[codecov-commenter]

Codecov Report

Merging #679 (26816f6) into master (a8acf0d) will not change coverage.
The diff coverage is n/a.

❗ Current head 26816f6 differs from pull request most recent head 9faea13. Consider uploading reports for the commit 9faea13 to get more accurate results

@@           Coverage Diff           @@
##           master     #679   +/-   ##
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  Coverage   93.59%   93.59%           
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  Files          76       76           
  Lines        2309     2309           
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  Hits         2161     2161           
  Misses        148      148