texview v0.0.3 - the fruity release

Now supporting macOS!

Other changes:

• Improved support for High-DPI Displays / displayscaling ("Retina").
  • Using a vector font for ImGui now that can be scaled to any size, instead of the builtin bitmap font.
• Errors and warnings (for example if a file couldn't be opened) are now shown in an overlay and can also be looked up in the Log Window, instead of only being printed to stderr where you'd only see them when starting texview in a terminal.
• The texture information (resolution, format, ...) in the sidebar can now be hidden.
• The imgui.ini file is now saved in your userdir (Linux: ~/.config/texview/, Windows: C:\Users\Horst\AppData\Roaming\texview\, macOS: ~/Library/Application Support/texview/).
• Using an OpenGL Core Profile now (instead of a compatibility profile with immediate mode GL; required for macOS).
• Building and linking only the decompressing parts of zstd now, for a much faster build and slightly smaller binaries
• Updated libktx

Many thanks to @michaeleggers for helping with the macOS support, and to @tomkidd / @MacSourcePorts for providing a notarized macOS binary!