LFKeyboards Mini1800: refactor into revisions (#16260)

* fork Mini1800 into reva and revc versions

* update info.json

- apply friendly formatting
- update maintainer value

* update keymap rules.mk formatting

- align inline comments
- convert tabs to spaces

* align keymap rules.mk files to QMK template

* move common keymap rules.mk settings to revision level

* info.json: correct key sequence

* align revision rules.mk files to QMK template

* clean up revision rules.mk files

* add readme files for each revision

* correct USB Product string

* remove post_rules.mk files

The internal settings were commented out, so the files actually don't do anything.

* edit Bootloader instructions on main readme

* move non-assignment rules to post_rules.mk

* add inline comments for NKRO_ENABLE per fauxpark

keyboards/lfkeyboards/mini1800/config.h

@@ -23,7 +23,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define PRODUCT_ID      0x6060
 #define DEVICE_VER      0x0001
 #define MANUFACTURER    LFKeyboards
-#define PRODUCT         LFK87
+#define PRODUCT         Mini1800
 
 #define DIODE_DIRECTION COL2ROW