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-convert.md

@@ -0,0 +1,37 @@
+# magick convert
+
+> Convert between image formats, scale, join, and create images, and much more.
+> Note: this tool (previously `convert`) has been replaced by `magick` in ImageMagick 7+.
+> More information: <https://imagemagick.org/script/convert.php>.
+
+- Convert an image from JPEG to PNG:
+
+`magick convert {{path/to/input_image.jpg}} {{path/to/output_image.png}}`
+
+- Scale an image to 50% of its original size:
+
+`magick convert {{path/to/input_image.png}} -resize 50% {{path/to/output_image.png}}`
+
+- Scale an image keeping the original aspect ratio to a maximum dimension of 640x480:
+
+`magick convert {{path/to/input_image.png}} -resize 640x480 {{path/to/output_image.png}}`
+
+- Scale an image to have a specified file size:
+
+`magick convert {{path/to/input_image.png}} -define jpeg:extent=512kb {{path/to/output_image.jpg}}`
+
+- Vertically/Horizontally append images:
+
+`magick convert {{path/to/image1.png path/to/image2.png ...}} {{-append|+append}} {{path/to/output_image.png}}`
+
+- Create a GIF from a series of images with 100ms delay between them:
+
+`magick convert {{path/to/image1.png path/to/image2.png ...}} -delay {{10}} {{path/to/animation.gif}}`
+
+- Create an image with nothing but a solid red background:
+
+`magick convert -size {{800x600}} "xc:{{#ff0000}}" {{path/to/image.png}}`
+
+- Create a favicon from several images of different sizes:
+
+`magick convert {{path/to/image1.png path/to/image2.png ...}} {{path/to/favicon.ico}}`