Major mode for editing systemd units. Similar to `conf-mode' but with enhanced highlighting; e.g. for specifiers and booleans. Employs strict regex for whitespace. Features a facility for browsing documentation: use C-c C-o to open links to documentation in a unit (cf. systemctl help). Supports completion of directives and sections in either units or network configuration. Both a completer for `completion-at-point-functions' and a company backend are provided. The latter can be enabled by adding `company-mode' to `systemd-mode-hook'.