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-montage.md

@@ -0,0 +1,25 @@
+# magick montage
+
+> Tile images into a customizable grid.
+> See also: `magick`.
+> More information: <https://imagemagick.org/script/montage.php>.
+
+- Tile images into a grid, automatically resizing images larger than the grid cell size:
+
+`magick montage {{path/to/image1.jpg path/to/image2.jpg ...}} {{path/to/montage.jpg}}`
+
+- Tile images into a grid, automatically calculating the grid cell size from the largest image:
+
+`magick montage {{path/to/image1.jpg path/to/image2.jpg ...}} -geometry {{+0+0}} {{path/to/montage.jpg}}`
+
+- Specify the grid cell size and resize images to fit it before tiling:
+
+`magick montage {{path/to/image1.jpg path/to/image2.jpg ...}} -geometry {{640x480+0+0}} {{path/to/montage.jpg}}`
+
+- Limit the number of rows and columns in the grid, causing input images to overflow into multiple output montages:
+
+`magick montage {{path/to/image1.jpg path/to/image2.jpg ...}} -geometry {{+0+0}} -tile {{2x3}} {{montage_%d.jpg}}`
+
+- Resize and crop images to fill their grid cells before tiling:
+
+`magick montage {{path/to/image1.jpg path/to/image2.jpg ...}} -geometry {{+0+0}} -resize {{640x480^}} -gravity {{center}} -crop {{640x480+0+0}} {{path/to/montage.jpg}}`