<, >, |, $: add page (#13846)

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>
Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/common/vertical-bar.md

@@ -0,0 +1,12 @@
+# Vertical bar
+
+> Pipe data between programs.
+> More information: <https://gnu.org/software/bash/manual/bash.html#Pipelines>.
+
+- Pipe `stdout` to `stdin`:
+
+`{{command}} | {{command}}`
+
+- Pipe both `stdout` and `stderr` to `stdin`:
+
+`{{command}} |& {{command}}`