Updating to ImGui 1.88

[njk42]

Hello, I love the concept of this meta-library to easily integrate ImGui and GLFW with other related packages. I installed it with CMake FetchPackage() as described in the README, but the version of ImGui it pulls in to my project is v1.80 WIP.

Are there simple instructions anywhere on how to rebuild Mahi-Gui but with the most recent commits of the dependent libraries like ImGui v1.88? Unfortunately, my application which runs fine in a stand-alone instance with ImGui 1.88 fetched via vcpkg suffers from a couple missing features and strange assert() failures after moving it into a Mahi-Gui instance based on the older ImGui 1.80. Thanks!