Add .gitattributes with rules for line endings of files.
Add .gitattributes with rules for line endings of files.

(cherry picked from commit f2a2be72b341f55c44a035b1257177d83489ea5c)

dougbinks/imgui,aimotive/imgui-glfw,dougbinks/imgui,nProtect/imgui,ocornut/imgui,burningreggae/imgui,ocornut/imgui,nProtect/imgui,nProtect/imgui,bkaradzic/imgui,burningreggae/imgui,ocornut/imgui,bkaradzic/imgui,ggtucker/imgui,bkaradzic/imgui,Flix01/imgui,ggtucker/imgui,aimotive/imgui-glfw,ggtucker/imgui,Flix01/imgui,Flix01/imgui