fix: add missing letter ё to the Russian keyboard layout (#469)

The Russian layout offered no way to type ё. Long-pressing the е key
only exposed the digit 5, and with the numbers row enabled the digit is
stripped from the popup, leaving no popup at all — so ё was untypeable.

Add ё to the popupCharacters of the е key, matching the existing
convention used elsewhere (e.g. the Belarusian layout's є, ґ, щ). The
Belarusian cyrillic layout already has a dedicated ё key, so it needs no
change.

Refs: https://github.com/FossifyOrg/Keyboard/issues/405

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- Fixed the letter ё being untypeable on the Russian keyboard; long-press the е key to type it ([#405])
 
 ## [1.9.1] - 2026-02-02
 ### Changed
@@ -170,6 +172,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#335]: https://github.com/FossifyOrg/Keyboard/issues/335
 [#356]: https://github.com/FossifyOrg/Keyboard/issues/356
 [#372]: https://github.com/FossifyOrg/Keyboard/issues/372
+[#405]: https://github.com/FossifyOrg/Keyboard/issues/405
 
 [Unreleased]: https://github.com/FossifyOrg/Keyboard/compare/1.9.1...HEAD
 [1.9.1]: https://github.com/FossifyOrg/Keyboard/compare/1.9.0...1.9.1

app/src/main/res/xml/keys_letters_russian.xml

@@ -63,7 +63,7 @@
         <Key
             app:keyLabel="е"
             app:keyWidth="9.05%p"
-            app:popupCharacters="5"
+            app:popupCharacters="5ё"
             app:popupKeyboard="@xml/keyboard_popup_template"
             app:topSmallNumber="5" />
         <Key