systemd-analyze: add security example, generalize scope of the tool, add link to manual page (#7161)

pages/linux/systemd-analyze.md

@@ -1,6 +1,8 @@
 # systemd-analyze
 
+> Analyze and debug system manager.
 > Show timing details about the boot process of units (services, mount points, devices, sockets).
+> More information: <https://manned.org/systemd-analyze>.
 
 - List time of each unit to start up:
 
@@ -17,3 +19,7 @@
 - Plot a dependency graph and convert it to an SVG file:
 
 `systemd-analyze dot | dot -T{{svg}} > {{path/to/file.svg}}`
+
+- Show security scores of running units:
+
+`systemd-analyze security`