sed: add delete and insert commands (#12124)

* sed: add delete and insert commands

---------

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/linux/sed.md

@@ -8,18 +8,26 @@
 
 `{{command}} | sed 's/apple/mango/g'`
 
-- Execute a specific script [f]ile and print the result to `stdout`:
-
-`{{command}} | sed -f {{path/to/script.sed}}`
-
 - Replace all `apple` (extended regex) occurrences with `APPLE` (extended regex) in all input lines and print the result to `stdout`:
 
 `{{command}} | sed -E 's/(apple)/\U\1/g'`
 
-- Print just a first line to `stdout`:
-
-`{{command}} | sed -n '1p'`
-
 - Replace all `apple` (basic regex) occurrences with `mango` (basic regex) in a specific file and overwrite the original file in place:
 
 `sed -i 's/apple/mango/g' {{path/to/file}}`
+
+- Execute a specific script [f]ile and print the result to `stdout`:
+
+`{{command}} | sed -f {{path/to/script.sed}}`
+
+- Print just the first line to `stdout`:
+
+`{{command}} | sed -n '1p'`
+
+- [d]elete the first line of a file:
+
+`sed -i 1d {{/path/to/file}}`
+
+- [i]nsert a new line at the first line of a file:
+
+`sed -i '1i\your new line text\' {{/path/to/file}}`