feat(shields): add tidbit and tidbit_19key shields

app/boards/shields/tidbit/README.md

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+# Building ZMK for the Tidbit
+
+Some general notes/commands for building standard tidbit layouts from the assembly documentation.
+
+## Standard "Non Dense" Build
+
+```
+west build -p -d build/tidbit/default --board nice_nano -- -DSHIELD=tidbit
+```
+
+## Dense "19 keys" Build
+
+```
+west build -p -d build/tidbit/19_key --board nice_nano -- -DSHIELD=tidbit_19key
+```
+
+## LED Notes
+
+If you built your tidbit without the LEDs _and_ are using a nice!nano board, you'll need to change the following in your local tidbit config or add them to the end of the file.
+
+```
+CONFIG_ZMK_RGB_UNDERGLOW=n
+CONFIG_WS2812_STRIP=n
+```
+
+## Encoder Notes
+
+If you built your tidbit without encoders, you'll need to change the following in your local tidbit config or add them to the end of the file.
+
+```
+CONFIG_EC11=n
+CONFIG_EC11_TRIGGER_GLOBAL_THREAD=n
+```
+
+## OLED Builds
+
+If using an OLED screen, you'll need to change the following in your local tidbit config or add them to the end of the file.
+
+```
+CONFIG_ZMK_DISPLAY=y
+```