Nano YAML Highlighting
By default, nano on Debian Buster does not support syntax highlighting YAML files. Adding this template to nano will give you syntax highlighting when opening YAML files in nano.
sudo tee /usr/share/nano/yaml.nanorc <<EOF >> /dev/null
# Supports `YAML` files
syntax "YAML" "\.ya?ml$"
header "^(---|===)" "%YAML"
## Keys
color magenta "^\s*[\$A-Za-z0-9_-]+\:"
color brightmagenta "^\s*@[\$A-Za-z0-9_-]+\:"
## Values
color white ":\s.+$"
## Booleans
icolor brightcyan " (y|yes|n|no|true|false|on|off)$"
## Numbers
color brightred " [[:digit:]]+(\.[[:digit:]]+)?"
## Arrays
color red "\[" "\]" ":\s+[|>]" "^\s*- "
## Reserved
color green "(^| )!!(binary|bool|float|int|map|null|omap|seq|set|str) "
## Comments
color brightwhite "#.*$"
## Errors
color ,red ":\w.+$"
color ,red ":'.+$"
color ,red ":".+$"
color ,red "\s+$"
## Non closed quote
color ,red "['\"][^['\"]]*$"
## Closed quotes
color yellow "['\"].*['\"]"
## Equal sign
color brightgreen ":( |$)"
EOF
