feat: ignore deprecated-enum-enum-conversion warnings in GCC (#706)

Ignore `deprecated-enum-enum-conversion` warnings in GCC. This fixes issue #688 for GCC users.

Author: samangh

implot.cpp

@@ -219,6 +219,7 @@ You can read releases logs https://github.com/epezent/implot/releases for more d
 #pragma clang diagnostic ignored "-Wenum-enum-conversion" // warning: bitwise operation between different enumeration types ('XXXFlags_' and 'XXXFlagsPrivate_') is deprecated
 #elif defined(__GNUC__)
 #pragma GCC diagnostic ignored "-Wformat-nonliteral"    // warning: format not a string literal, format string not checked
+#pragma GCC diagnostic ignored "-Wdeprecated-enum-enum-conversion" // warning: bitwise operation between different enumeration types ('XXXFlags_' and 'XXXFlagsPrivate_') is deprecated
 #endif
 
 // Global plot context