Add script to make a movie from simulation images (#779)

### Description
This adds a Bash script to process a sequence of image files (`*.png`)
in the current working directory into a H.264-encoded `*.mov` movie,
with a text annotation for consistent branding of Quokka simulation
movies.

### Related issues
N/A

### Checklist
_Before this pull request can be reviewed, all of these tasks should be
completed. Denote completed tasks with an `x` inside the square brackets
`[ ]` in the Markdown source below:_
- [x] I have added a description (see above).
- [x] I have added a link to any related issues see (see above).
- [x] I have read the [Contributing
Guide](https://github.com/quokka-astro/quokka/blob/development/CONTRIBUTING.md).
- [ ] I have added tests for any new physics that this PR adds to the
code.
- [ ] I have tested this PR on my local computer and all tests pass.
- [ ] I have manually triggered the GPU tests with the magic comment
`/azp run`.
- [x] I have requested a reviewer for this PR.

scripts/make_movie.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+CONVERT_EXE=$(which convert)  # install with: "spack install imagemagick"
+RENAME_EXE=$(which rename)    # install with: "spack install rename"
+FFMPEG_EXE=$(which ffmpeg)    # install with: "spack install ffmpeg+libx264+drawtext"
+
+set -x
+
+## rename *.png files
+
+$RENAME_EXE 's/\d+/sprintf("%07d",$&)/e' -- *.png
+
+## resize frames
+
+for file in *.png;
+do
+    $CONVERT_EXE $file -resize 2048x2048 $(basename -s .png $file).resize_large.png
+done
+
+## make movie
+FPS=10
+FILTERS="pad=ceil(iw/2)*2:ceil(ih/2)*2:color=white, drawtext=fontfile=/usr/share/fonts/google-droid/DroidSans.ttf:text='QUOKKA Simulation':fontcolor=white:fontsize=48:box=1:[email protected]:boxborderw=5:x=0.9*(w-text_w):y=0.9*(h-text_h)"
+
+$FFMPEG_EXE -framerate $FPS -pattern_type glob -i "*.resize_large.png" -r $FPS -vcodec libx264 -vf "$FILTERS" -pix_fmt yuv420p -preset slow -tune animation -crf 18 movie_large.mov