move @npspears 's boards into /checkerboards (#16100)

keyboards/checkerboards/plexus75/readme.md

@@ -10,6 +10,6 @@ The Plexus75 is a 60% ortholinear keyboard based on the XD75 but instead of an a
 
 Make example for this keyboard (after setting up your build environment):
 
-    make plexus75:default
+    make checkerboards/plexus75: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).

keyboards/checkerboards/pursuit40/readme.md

@@ -10,6 +10,6 @@ The Pursuit40 PCB is a modified layout Panc40 by Alex Panc. It's similar to trad
 
 Make example for this keyboard (after setting up your build environment):
 
-    make pursuit40:default
+    make checkerboards/pursuit40: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).

keyboards/checkerboards/quark/readme.md

@@ -10,6 +10,6 @@ The Quark PCB is a modified layout for the Planck by OLKB. It's similar to a Pla
 
 Make example for this keyboard (after setting up your build environment):
 
-    make quark:default
+    make checkerboards/quark: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).