Update 19-collaboration-tools.md #211

	name: Check Lowercase Filenames
	# see issue #82
	# "So I changed all the filenames containing capital letters to lower case.
	# However, since the initial opening of this ticket, more files with upper case letter had been added. I renamed them too.
	# But this shows that we need a systematic solution to this, otherwise we will run into this problem again and again.
	# Could a check like this be done with GitHub Actions?"

	on:
	pull_request:
	types: [opened, synchronize, reopened]
	push:
	branches:
	- main

	jobs:
	check_lowercase:
	runs-on: ubuntu-latest
	steps:
	- name: Checkout code
	uses: actions/checkout@v3

	- name: Check for uppercase filenames
	run: \|
	error=0
	while IFS= read -r file; do
	basename=$(basename "$file")
	if [[ "$basename" =~ [A-Z] ]]; then
	echo "Error: The file '$file' contains uppercase letters (this results in crashes with 'View on Github' button)."
	error=1
	fi
	done < <(find . -type f -iname '*.md' \| grep -E '^./docs/')
	if [ "$error" -eq 1 ]; then
	exit 1
	else
	echo "All basenames are lowercase."
	fi

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