schroot: add session examples, move `--list` to the top (#10650)

Listing all available chroots is often one of the first things users need to
do. Make it the first example.

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>
Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/linux/schroot.md

@@ -1,8 +1,12 @@
 # schroot
 
-> Run command or start an interactive shell with a different root directory. More customizable than `chroot`.
+> Run a command or start an interactive shell with a different root directory. More customizable than `chroot`.
 > More information: <https://wiki.debian.org/Schroot>.
 
+- List available chroots:
+
+`schroot --list`
+
 - Run a command in a specific chroot:
 
 `schroot --chroot {{chroot}} {{command}}`
@@ -19,6 +23,14 @@
 
 `schroot --chroot {{chroot}} --user {{user}}`
 
-- List available chroots:
+- Begin a new session (a unique session ID is returned on `stdout`):
 
-`schroot --list`
+`schroot --begin-session --chroot {{chroot}}`
+
+- Connect to an existing session:
+
+`schroot --run-session --chroot {{session_id}}`
+
+- End an existing session:
+
+`schroot --end-session --chroot {{session_id}}`