tac: refresh page (#8057)

* More general descriptions and better title

* Don't use `print` word

* More specific verb in first sample description:

- `display` -> `concatenate`

* Add `-b`/`-r`/`-s` examples

* Duplicate `tac` to `linux/`

* Highlight first option chars

* Add `See also` reference

pages/linux/tac.md

@@ -0,0 +1,25 @@
+# tac
+
+> Display and concatenate files with lines in reversed order.
+> See also: `cat`.
+> More information: <https://www.gnu.org/software/coreutils/tac>.
+
+- Concatenate specific files in reversed order:
+
+`tac {{path/to/file1 path/to/file2 ...}}`
+
+- Display `stdin` in reversed order:
+
+`{{cat path/to/file}} | tac`
+
+- Use a specific separator:
+
+`tac --separator {{,}} {{path/to/file1 path/to/file2 ...}}`
+
+- Use a specific regex as a separator:
+
+`tac --regex --separator {{[,;]}} {{path/to/file1 path/to/file2 ...}}`
+
+- Use a separator before each file:
+
+`tac --before {{path/to/file1 path/to/file2 ...}}`