feat: add a short example of using grep on a non-N string and showing grep -c

[ameynert]

Closes #314

Adds a short example of using grep with a non-N string and introduces grep -c.

[github-actions]

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 04-redirection.md | 13 +++++++++++++
 md5sum.txt        |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

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⏱️ Updated at 2025-05-23 16:59:08 +0000

[TaylorKT]

Looks like a great addition!