Add pcewing Speedo v3 keymap (#18118)

* Add pcewing Speedo v3 keymap

* Add readme and code quality improvements

users/pcewing/README.md

@@ -0,0 +1,85 @@
+# User Space Code for Paul Ewing
+
+This folder contains my user space code.
+
+## Key Repeater
+
+I've implemented a key repeater utility in [./key_repeater.h](./key_repeater.h)
+and [./key_repeater.c](./key_repeater.c) that is similar in concept to the
+"rapid fire" feature many game controllers come with. The intent behind this is
+that the user can hold down a key and while it is pressed, a keycode will be
+repeatedly sent. I have found this useful in certain games and during game
+development.
+
+The duration of the key press as well as the time between key presses is
+slightly randomized by design. This is to simulate more realistic human
+behavior. By setting the minimum and maximum duration fields to the same value
+in the configuration, this randomization can be disabled.
+
+**Note:** Please be aware that this might be against the terms of service in
+certain games so use your own discretion before using this feature.
+
+### How to Use
+
+Define the repeater and then configure and allocate it in your keymap's
+initialization process:
+
+```c
+static struct key_repeater_t* click_repeater = NULL;
+
+void keyboard_post_init_user(void) {
+    // Seed the random number generator which is used by the key repeater
+    srand(timer_read32());
+
+    // Configure and instantiate a key repeater for mouse button 1 "rapid fire"
+    struct key_repeater_config_t cfg = {
+        .key = KC_BTN1,             // Press mouse button 1 (Left click)
+        .key_duration_min = 20,     // Press key for 20 to 50 milliseconds
+        .key_duration_max = 50,
+        .wait_duration_min = 90,    // Wait for 90 to 140 milliseconds before pressing again
+        .wait_duration_max = 140,
+    };
+
+    click_repeater = kr_new(&cfg);
+}
+```
+
+Make sure the key repeater is polled during matrix scanning:
+
+```c
+void matrix_scan_user(void) {
+    kr_poll(click_repeater);
+}
+```
+
+Define a custom keycode that will enable/disable the repeater: 
+
+```c
+enum {
+    RP_BTN1 = SAFE_RANGE, // Click repeatedly while key is held
+};
+```
+
+Assign the keycode to a key in your `LAYOUT(...)` macro.
+
+Define the logic to enable/disable the repeater when the custom keycode is
+pressed or released:
+
+```c
+bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+    switch (keycode) {
+    case RP_BTN1:
+        if (record->event.pressed) {
+            kr_enable(click_repeater);
+        } else {
+            kr_disable(click_repeater);
+        }
+        return false;
+    default:
+        return true;
+    }
+}
+```
+
+For a full working example in own of my own keymaps, see:
+[keyboards/cozykeys/speedo/v3/keymaps/pcewing/keymap.c](../../keyboards/cozykeys/speedo/v3/keymaps/pcewing/keymap.c)