ImGui-SFML 2.6 (#252)

ImGui-SFML 2.5

Small release to fix broken vcpkg package (see microsoft/vcpkg#21530)
* Remove type alias for ImTextureID (#186) (thanks, @JackBoosY)

ImGui-SFML 2.4

* Don't update io.KeysDown for keys which Dear ImGui doesn't care about
  - fixes some crashes when pressing keys which Dear ImGui doesn't process
* Multiple window/Dear ImGui context support (thanks, @emrsmsrli)
* Support #define ImDrawIdx unsigned int in renderer via imconfig.h (thanks, @Doy-lee)
* Fix android delete/backspace keycodes (thanks, @Alia5)

ImGui-SFML 2.3

* Fix 'bgColor' not being passed to 'ImGui::ImageButton' (thanks, @SuperV1234)
* Fix KeysDown not being reset to 'false' when losing focus
* Sync OpenGL rendering code with Dear ImGui's OpenGL2 backend implementation

ImGui-SFML v2.2

This release is an accumulation small things which are important to release:
* ImGui >= 1.80 is now required. ImGui added imgui_tables.cpp and some
of the functions were deprecated. It's important to stay up-to-date
* Fixed Image/ImageButton and sf::RenderTexture problems (texture was
shown upside down)
* Removed an overload for Image/ImageButton which took sf::Texture and
sf::IntRect textureRect. You should use sf::Sprite now.
* Added sf::Cursor::Hand (thanks, @DarkContact)
* Restored C++03 support
* Fix MSVC warnings (thanks, @andrew-gresyk, @plutphil)

Also I'd like to thank @pinam45 for making CI for ImGui-SFML. Also
thanks to @sabidib, @dubgron and @ComicSansMS for improving/fixing
builds and CMake scripts.

ImGui-SFML v2.1

* Can now use ImGui-SFML without sf::RenderTarget
* Add Conanfile for packaging (thanks, @barsoosayque)
* Fix clipboard for unicode strings (thanks, @Lomadriel)
* Add horizonal wheel support (thanks, @Melix19)
* Set SFML_STATIC_LIBRARIES to ON when BUILD_SHARED_LIBS is OFF (thanks, @saliainfo)

Use MouseWheelScrollEvent instead of MouseWheelMoveEvent

Fixes #83

Set io.BackendPlatformName in Init

Merge branch 'develop'

ImGui-SFML v.2.0
* Better CMake support
* Compiler warning fixes
* Can now compile as shared library

Merge pull request #43 from ekunuke/master

Fix DrawRectFilled calling wrong draw_list function.