add backtick quotes for code snippets

* Added for keycodes, pin numbers, and code snippets. Mostly in tables.
* Enhance documentation readability
* Make automated spell checking easier - aspell automatically ignores these snippets
* fix invalid markdown table in mouse_keys.md

hardware/README.md

@@ -5,31 +5,31 @@
 This board adapts the pinout of a Circuit Python compatible [Adafruit ItsyBitsy M4 Express](https://www.adafruit.com/product/3800) to that of the [SparkFun Pro Micro](https://www.sparkfun.com/products/12640) to allow the ItsyBitsy to be used with the many keyboards that support the footprint of the Pro Micro.
 
 ## Pin mapping
-Pro Micro Pin | ItsyBitsy Pin
------------- | -------------
-TX0/PD3 | TX
-RX1/PD2 | RX
-GND | GND
-GND | GND
-2/PD1 | SDA
-3/PD0 | SCL
-4/PD4 | D13
-5/PC6 | D12
-6/PD7 | D11
-7/PE6 | D10
-8/PB4 | D9
-9/PB5 | D7
-Raw | 
-GND | GND
-RST | RST
-VCC | USB
-A3/PF4 | A0
-A2/PF5 | A1
-A1/PF6 | A2
-A0/PF7 | A3
-15/PB1 | A4
-14/PB3 | A5
-16/PB2 | SCK
+| Pro Micro Pin   | ItsyBitsy Pin   |
+|-----------------|-----------------|
+| `TX0/PD3`       | `TX`            |
+| `RX1/PD2`       | `RX`            |
+| `GND`           | `GND`           |
+| `GND`           | `GND`           |
+| `2/PD1`         | `SDA`           |
+| `3/PD0`         | `SCL`           |
+| `4/PD4`         | `D13`           |
+| `5/PC6`         | `D12`           |
+| `6/PD7`         | `D11`           |
+| `7/PE6`         | `D10`           |
+| `8/PB4`         | `D9`            |
+| `9/PB5`         | `D7`            |
+| `Raw`           |                 |
+| `GND`           | `GND`           |
+| `RST`           | `RST`           |
+| `VCC`           | `USB`           |
+| `A3/PF4`        | `A0`            |
+| `A2/PF5`        | `A1`            |
+| `A1/PF6`        | `A2`            |
+| `A0/PF7`        | `A3`            |
+| `15/PB1`        | `A4`            |
+| `14/PB3`        | `A5`            |
+| `16/PB2`        | `SCK`           |
 
 
 ## So how do I use it?