pamslice: add page (#12397)

* pamslice: add page

* Update pages/common/pamslice.md

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/pamslice.md

@@ -0,0 +1,20 @@
+# pamslice
+
+> Extract one line of values out of a PAM image.
+> More information: <https://netpbm.sourceforge.net/doc/pamslice.html>.
+
+- Print the values of the pixels in the n'th row in a table:
+
+`pamslice -row {{n}} {{path/to/image.pam}}`
+
+- Print the values of the pixels in the n'th column in a table:
+
+`pamslice -column {{n}} {{path/to/image.pam}}`
+
+- Consider the m'th plane of the input image only:
+
+`pamslice -row {{n}} -plane {{m}} {{path/to/image.pam}}`
+
+- Produce output in a format suitable for input to an `xmgr` for visualisation:
+
+`pamslice -row {{n}} -xmgr {{path/to/image.pam}}`