[Keymap] Reorganization, cleanup and readmes for drashna code (#15617)

users/drashna/split/readme.md

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+# Custom Split Transport
+
+To disable the customized split transport, add `CUSTOM_SPLIT_TRANSPORT_SYNC = no` to your `rules.mk`.
+
+This syncs a number of additional settings, such as the keymap_config (magic settings), user eeprom configs, and misc firmware settings. 
+
+Additionally, this supports a watchdog timer reset for the secondary split side. 
+
+## User State Config 
+
+The User states that it sync are: 
+
+* Audio Enable status
+* Audio Clicky states
+* Unicode mode
+* Pointing Device tap toggle status
+* Swap Hands status
+* Host Driver status
+
+## Userspace Config
+
+The userspace config states that are synced are: 
+
+* RGB layer indication
+* "is overwatch" status
+* nuke switch
+* Swapped numbers
+* RGB Matrix idle animation
+* Autocorrect enable status