Add simplistic editor to samples to showcase TextEditingDeltas (#1217)

* Add simplistic editor to samples

* Toggle styles fix

* update name

* Add to CI and dependabot

* update minimum dart sdk

* fix pubspec

* update README

* Update README

* Add shift + arrow key selection and copy/paste keyboard actions

* Update README.md

* copy edits to readme

includes a sentence in each layer description whose accuracy I still need to verify

* update pubspec

* update pubspec.lock

* Fix bug with disabling expansion of replacement when cursor is at edge of replacement

Co-authored-by: Renzo Olivares <roliv@google.com>
Co-authored-by: Craig Labenz <craig.labenz@gmail.com>

simplistic_editor/android/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Fri Jun 23 08:50:38 CEST 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.4-all.zip