gifsicle: improve description and examples (#12247)

* gifsicle: improve description and examples

---------

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/common/gifsicle.md

@@ -1,19 +1,19 @@
 # gifsicle
 
-> GIF manipulator.
+> Create, edit, manipulate, and get information about GIF files.
 > More information: <https://www.lcdf.org/gifsicle>.
 
 - Optimize a GIF as a new file:
 
 `gifsicle {{path/to/input.gif}} --optimize=3 -o {{path/to/output.gif}}`
 
-- Unoptimize a GIF in place:
+- Use [b]atch mode (modify each given file in place) and unoptimize a GIF:
 
 `gifsicle -b {{path/to/input.gif}} --unoptimize`
 
 - Extract a frame from a GIF:
 
-`gifsicle {{path/to/input.gif}} '#{{0}}' > {{path/to/firstframe.gif}}`
+`gifsicle {{path/to/input.gif}} '#{{0}}' > {{path/to/first_frame.gif}}`
 
 - Make a GIF animation from selected GIFs:
 
@@ -27,6 +27,6 @@
 
 `gifsicle -b {{path/to/input.gif}} --delete '#{{0-9}}' '#{{20-}}'`
 
-- Modify all frames of a GIF using specific transformation options:
+- Modify all frames by cropping them to a rectangle, changing their scale, flipping them, and rotating them:
 
-`gifsicle -b --crop {{50}},{{50}}+{{-50}}x{{-50}} --scale {{0.25}} --flip-horizontal --rotate-90 {{path/to/input.gif}}`
+`gifsicle -b --crop {{starting_x}},{{starting_y}}+{{rect_width}}x{{rect_height}} --scale {{0.25}} --flip-horizontal --rotate-{{90|180|270}} {{path/to/input.gif}}`