Rename keyboard-level readmes to lower-case (#10759)

This is the recommendation in the [PR
Checklist](https://docs.qmk.fm/#/pr_checklist?id=keyboard-prs) and it
will make working with them easier in the CLI/API/etc.

keyboards/handwired/aplx2/readme.md

@@ -0,0 +1,34 @@
+# Aplx2
+
+![Front](https://i.imgur.com/cN4WfaQl.jpg)  
+   
+A simple 2% keyboard for osu!. Designed to be assembled as a sandwich with a Pro Micro, using M3 x 16mm screws, your choice of MX- or Alps-compatible switches, and 1N4148 diodes.   
+
+**Layout:**  
+The default layout is: Z , X .
+Used pins can be found in `config.h`. All ProMicro pins can be found [here](https://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/ProMicro16MHzv1.pdf).
+
+* Keyboard Maintainer: [Aplyard](https://github.com/Aplyard)
+* Hardware Supported: Pro Micro (ATmega32U4)
+* Hardware Availability: [GitHub](https://github.com/Aplyard/Aplx2), [Thingiverse](https://www.thingiverse.com/thing:4294608)
+
+Make example for this keyboard (after setting up your build environment):
+
+     make handwired/aplx2:default
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
+
+---  
+**Designed in:**  
+Fusion360     
+[Keyboard Plate & Case Builder](http://builder.swillkb.com/)  
+ 
+
+**Usefull Links:**  
+[Qmk Online Configurator](https://config.qmk.fm/#)  
+
+**Alternatives of qmk that worked for me:**  
+[Keyboard Layout Editor](http://www.keyboard-layout-editor.com/#/)   
+[Firmware Builder](https://kbfirmware.com/)      
+
+---