[Keymap] Added userspace for d4mation. Included their keymap for the Atreus62 (#7483)

* Added userspace for d4mation. Included their keymap for the Atreus62

* Do not assign layer numbers manually

* Remove some unneeded things per @drashna's recommendation

* Fix some single line comments I missed

* Update unicode macros to use send_unicode_hex_string() instead of process_unicode()

* OBetter check for Unicode Enabled. Moved some checks into macros.c

* Use eeconfig_init_user() to set default unicode input mode

users/d4mation/tap-hold.c

@@ -0,0 +1,28 @@
+#include "tap-hold.h"
+
+#ifndef TAP_HOLD_TIME
+#define TAP_HOLD_TIME 200
+#endif
+
+uint16_t tap_hold_timer;
+
+void tap_or_hold( keyrecord_t *record, uint16_t tap, uint16_t hold ) {
+
+  if ( record->event.pressed ) {
+    tap_hold_timer = timer_read();
+  } else {
+
+    if ( tap_hold_timer &&
+      timer_elapsed( tap_hold_timer ) > TAP_HOLD_TIME ) {
+      /* Held down then released */
+      tap_code( hold );
+    } else {
+      /* Quickly Tapped */
+      tap_code( tap );
+    }
+
+    tap_hold_timer = 0;
+
+  }
+
+}