add gif recorder to readme.md method

tools/FILM-GIFS-FOR-README.md

@@ -0,0 +1,22 @@
+# Record GIFs for README.md files
+
+On Fedora I use [wf-recorder](https://github.com/ammen99/wf-recorder) for recording screen to mp4, and [ffmpeg](https://www.ffmpeg.org/about.html) for post processing to .gif.
+
+```bash
+wf-recorder -g "$(slurp)" \
+  -f <MP4-FILE-NAME>.mp4 \
+  -c libx264 \
+  -r 30 \
+  -p crf=18 \
+  -p preset=slow
+```
+
+like something like this
+```bash
+ ffmpeg -i hagfish.mp4 \
+  -vf "fps=15,scale=920:-1:flags=lanczos,split[s0][s1];[s0]palettegen=max_colors=256:stats_mode=diff[p];[s1][p]paletteuse=dither=sierra2_4a" \
+  -loop 0 \
+  hagfish.gif
+```
+
+keep the scale at 920, I think it looks good on Gitea and probably GitHub