chore: standardize # style headers

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

docs/static/setup.ps1

@@ -1,5 +1,4 @@
 # Copyright (c) 2020 The ZMK Contributors
-#
 # SPDX-License-Identifier: MIT
 
 $ErrorActionPreference = "Stop"

docs/static/setup.sh

@@ -1,7 +1,6 @@
 #!/bin/bash
 
 # Copyright (c) 2020 The ZMK Contributors
-#
 # SPDX-License-Identifier: MIT
 
 set -e