kernel: rename extensions/ to kexts/

kexts/hello-world/extension.yaml

@@ -1,4 +1,7 @@
 name: hello-world
+description: |
+  A sample kernel extension, demonstrating the structure of a kext.
+  No actual functionality.
 id: net.doorstuck.socks.hello-world
 license: BSD-3-Clause
 copyright: Copyright © Max Wash 2023

kexts/hello-world/hello-world.c

@@ -0,0 +1,8 @@
+#include <socks/printk.h>
+#include <socks/kext.h>
+
+kern_status_t online(struct kext *self)
+{
+	printk("Hello, world!");
+	return KERN_OK;
+}