Add some generic/sparse readmes to get rid of errors (#3048)

keyboards/chibios_test/readme.md

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+# ChibiOS Test Keyboards
+
+Test code for several ARM based ChibiOS boards

keyboards/chibios_test/stm32_f072_onekey/readme.md

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+# ChibiOS Test
+
+Test code for the stm32_f072 one key keyboard

keyboards/chibios_test/stm32_f103_onekey/readme.md

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+# ChibiOS Test
+
+Test code for the stm32_f103 one key keyboard

keyboards/chibios_test/teensy_lc_onekey/readme.md

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+# ChibiOS Test
+
+Test code for the teensy lc one key keyboard