v0.2.5

Changes since v0.2.4

• Updated the bundled libui-ng libraries to commit 09b83fb1.
• Added bindings for the pre-build uiVersion, uiControlOnDestroyed, uiControlSetMinimumSize, and uiGridDelete APIs.
• Made LibUI.version return a Ruby string.
• Fixed native gem packaging and the image table example.
• Updated CI and release jobs for current Ruby versions. The minimum supported Ruby version is now 2.7.