imagemagick: update pages (#12874)

* compare, convert, identify, import, mogrify, montage:
   move pages to subcommands of `magick`, create alias pages

* convert: add deprecation notice

---------

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

pages/common/magick-identify.md

@@ -0,0 +1,17 @@
+# magick identify
+
+> Describe the format and characteristics of image files.
+> See also: `magick`.
+> More information: <https://imagemagick.org/script/identify.php>.
+
+- Describe the format and basic characteristics of an image:
+
+`magick identify {{path/to/image}}`
+
+- Describe the format and verbose characteristics of an image:
+
+`magick identify -verbose {{path/to/image}}`
+
+- Collect dimensions of all JPEG files in the current directory and save them into a CSV file:
+
+`magick identify -format "{{%f,%w,%h\n}}" {{*.jpg}} > {{path/to/filelist.csv}}`