ignore/types: add Kconfig

Kconfig files are used to represent the configuration database of
Kbuild build system. Kbuild is developed as part of the Linux kernel.
There are numerous other users including OpenWrt and U-Boot.

Ref: https://docs.kernel.org/kbuild/index.html

Closes #2942

crates/ignore/src/default_types.rs

@@ -117,6 +117,7 @@ pub(crate) const DEFAULT_TYPES: &[(&[&str], &[&str])] = &[
     (&["julia"], &["*.jl"]),
     (&["jupyter"], &["*.ipynb", "*.jpynb"]),
     (&["k"], &["*.k"]),
+    (&["kconfig"], &["Kconfig", "Kconfig.*"]),
     (&["kotlin"], &["*.kt", "*.kts"]),
     (&["lean"], &["*.lean"]),
     (&["less"], &["*.less"]),