[Keymap] Add issmirnov {user, ergodox, levinson} files. (#7239)

* Add issmirnov {user, ergodox, levinson} files.

There are enough interesting QMK tricks in these layouts that it seems
worth it to share with the broader community. Big thanks to Drashna for
inspiration, as well as all the wonderful creators of QMK documentation.

Some highlights:
- Common layout shared between levinson and ergodox_ez
- TAP_TOG macro for fast layer switching
- Autogenerated keymaps ascii art with git hooks

I will do my best to do periodic rolls here, but the source of truth
will always be https://github.com/issmirnov/qmk-keebs

* Incorporate review feedback.

- Remove CLEAR_EEPROM in favor of built in EEP_RST
- Remove custom handlers for audio on bootup and shutdown
- Remove plethora of unneeded includes
- Remove deprecated and dupliated config options

HUGE thanks to drashna for the review!

* Apply suggestions from code review

Huge thanks to drashna@ for a very thorough review and the very useful suggestions.

Co-Authored-By: Drashna Jaelre <drashna@live.com>

* Remove unclear optimization

This was an artifact from some other keymap I saw.

1 files changed, 52 insertions, 0 deletions

diff --git a/users/issmirnov/tap_tog.c b/users/issmirnov/tap_tog.c
new file mode 100644
index 0000000000..02cea08b1d
--- /dev/null
+++ b/users/issmirnov/tap_tog.c
@@ -0,0 +1,52 @@
+#include QMK_KEYBOARD_H
+
+#include "tap_tog.h"
+
+bool tap_tog_layer_other_key_pressed = false;
+bool tap_tog_layer_toggled_on = false;
+uint8_t tap_tog_count = 0;
+
+void process_tap_tog(uint8_t layer, keyrecord_t *record) {
+  tap_tog_count++;
+  // press
+  if (record->event.pressed) {
+
+    // TTL has already been pressed and we are toggled into that layer
+    // so now we need to leave
+    if(tap_tog_layer_toggled_on) {
+      layer_clear();
+      tap_tog_layer_toggled_on = false;
+    }
+
+    // this means we're in our default layer
+    // so switch the layer immediately
+    // whether we'll switch back when it's released depends on if a button gets pressed while this is held down
+    else {
+      // switch layer
+      layer_on(layer);
+      tap_tog_layer_other_key_pressed = false; // if this becomes true before it gets released, it will act as a held modifier
+    }
+  }
+
+  // release
+  else {
+    // if it was used as a held modifier (like traditional shift)
+    if(tap_tog_layer_other_key_pressed) {
+      // switch layer back
+      layer_clear();
+    }
+    // if it was used as a toggle button
+    else {
+      // next time, it will turn layer off
+      tap_tog_layer_toggled_on = true;
+
+      // If it's been tapped twice, reset the toggle flag.
+      // Otherwise, we get stuck oscillating between this code block and the
+      // pressed && TTL_toggled_on block.
+      if (tap_tog_count >= 4 ) {
+        tap_tog_count = 0;
+        tap_tog_layer_toggled_on = false;
+      }
+    }
+  }
+}