install.sh: deal with capitalized docker user being interpreted as a host

Author: Williangalvani

install/install.sh

@@ -3,7 +3,7 @@
 # Set desired version to be installed
 VERSION="${VERSION:-master}"
 GITHUB_REPOSITORY=${GITHUB_REPOSITORY:-bluerobotics/blueos-docker}
-DOCKER_USER=${DOCKER_USER:-$(echo $GITHUB_REPOSITORY | cut -d'/' -f1)}
+DOCKER_USER=${DOCKER_USER:-$(echo $GITHUB_REPOSITORY | cut -d'/' -f1 | tr '[:upper:]' '[:lower:]')}
 REMOTE="${REMOTE:-https://raw.githubusercontent.com/${GITHUB_REPOSITORY}}"
 ROOT="$REMOTE/$VERSION"