[Keymap] ISO keymap for TADA68 with programming in mind (#6597)

* Layout with better use of navigation keys

* Update keyboards/tada68/keymaps/onelivesleft/config.h

Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>

keyboards/tada68/keymaps/onelivesleft/readme.md

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+# onelivesleft TADA68 layout for ISO UK
+
+This is a layout designed with programming in mind.  It's a modification of the `iso-uk` layout, and has been tested on a TADA68 purchased from kbdfans in May 2019. The physical key layout includes the "double height" iso Enter key and the "short" Left Shift along side the iso Backslash key. [See this keyboard-layout-editor.com Gist](http://www.keyboard-layout-editor.com/#/gists/acf0f32f7ea0d0ed35c901663ca47919)
+
+## Layout features:
+
+### Navigation column, from top-right down
+
+Bare:
+* Delete
+* Capslock
+* Home
+* End
+
+With FN:
+* Insert
+* Break
+* Page Up
+* Page Down
+
+### Mouse
+* Fn + cursors to move
+* Fn + Right Ctrl for left click
+* Fn + Right Shift for right click
+
+### Misc
+* Capslock key used as a second Fn key (for easy one-handed alt+F4 etc.)
+* Fn + ': `
+* Fn + P: Printscreen
+
+
+## Installation
+
+Please see the [tada68 readme](../../readme.md) using the following command
+
+```
+make tada68:onelivesleft:flashbin
+```