* Add interconnect details.
* Add m60 and nrf52840_m2 metadata files.

Renames instances of `readme.md` to `README.md` so that it's easily noticed.

PR: #561

Changes made with regex plus some manual tweaks.

Find:
/(?:(?<!#!\/bin\/sh\n)(?:^#\n))*^#.*?[Cc]opyright.*?(\d{4}) *([0-9A-z,_\- ]+).*?\n(?:^#\n)*^#.*?SPDX-License-Identifier:? *(.+) *?\n(?:^#\n)*/gm

Replace:
# Copyright (c) $1 $2
# SPDX-License-Identifier: $3

PR: #564

Aligns *.h and *.c to underscore naming convention.

These were kept (with warnings) for backwards compatibility with external boards/shields:
- kscan-mock.h
- matrix-transform.h
They should be removed in the future.

PR: #523

Ran all the default keymaps through the keymap upgrader and manually adjusted
alignment.

* Favor the settings reset images for this.

* Updated M60 keymap
* Make nrfjproj as default runner
* Remove the polling config