feat: Implement OLED display support and custom icons for 128x32 displays

- Added OLED functionality in keymap.c with custom rendering for layers and modifiers.
- Created a Python script to generate simple icons for OLED displays.
- Introduced a new rules.mk file to enable OLED features for the keymap.
- Developed an OLED font helper script for visualizing and designing custom graphics.
- Redesigned OLED layout to fit 128x32 displays, optimizing space for logos and layer indicators.
- Implemented flow tap functionality in flow_tap.c for enhanced key responsiveness.

users/smathev/flow_tap.c

@@ -0,0 +1,20 @@
+#include "keymap_danish.h"
+
+bool is_flow_tap_key(uint16_t keycode) {
+    if ((get_mods() & (MOD_MASK_CG | MOD_BIT_LALT)) != 0) {
+        return false; // Disable Flow Tap on hotkeys.
+    }
+    switch (get_tap_keycode(keycode)) {
+        case KC_SPC:
+        case KC_A ... KC_Z:
+        case KC_DOT:
+        case KC_COMM:
+        case DK_SCLN:
+        case DK_SLSH:
+        case DK_ARNG:
+        case DK_OSTR:
+        case DK_AE:
+            return true;
+    }
+    return false;
+}