add a dev page on how to make a gif (#3012)

docs/contributing/making-a-gif.md

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+# Making a pwndbg gif
+
+## The rundown
+
+If you wish to make a gif of your terminal while using pwndbg (usually to add an example of some command/workflow to the website) you should use [charmbracelet/vhs](https://github.com/charmbracelet/vhs). This ensures a consistent look to the gifs throughout the documentation, makes them easily updateable when UI changes are made, and just makes them more easily reproducable and modifiable in general.
+
+The workflow to creating a gif is simple. Start a recording:
+```{.bash .copy}
+vhs record > my_thingy.tape
+```
+Whatever you now do in the terminal will be "recorded" to the `my_thingy.tape` file. Exit the shell to save the recording. The tape probably isn't ready to use as-is. You will want to add some metadata and fixup some lines.
+??? example
+
+    This is the tape used to generate the gif at https://pwndbg.re/ :
+    ```bash
+    Output my_thingy.gif
+
+    Set FontSize 20
+    Set Width 1920
+    Set Height 1080
+    Set TypingSpeed 100ms
+
+    Sleep 1s
+    Type "gdb /bin/sh --quiet"
+    Enter
+    Sleep 2s
+    Type "start"
+    Enter
+    Sleep 3s
+    Type "ni"
+    Sleep 2s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Type "nextcall"
+    Sleep 3s
+    Enter 1
+    Sleep 10s
+    Type "b *$rdi"
+    Sleep 1s
+    Enter 1
+    Sleep 2s
+    Type "continue"
+    Sleep 1s
+    Enter 1
+    Sleep 4s
+    Type "nextcall"
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Enter 1
+    Sleep 1s
+    Type "stepsyscall"
+    Sleep 1s
+    Enter 1
+    Sleep 10s
+    Type "checksec"
+    Sleep 1s
+    Enter 1
+    Sleep 5s
+    Type "vmmap"
+    Sleep 1s
+    Enter 1
+    Sleep 5s
+    Type "exit"
+    Sleep 1s
+    Enter
+    Sleep 2s
+    ```
+
+You may now run
+```{.bash .copy}
+vhs my_thingy.tape
+```
+and it will generate a gif with the filename you specified in the tape (the `Output` line in the example).
+
+Make sure to commit the `.tape` file along with the gif.
+
+## Recording in Docker
+
+If the setup for the gif is not highly involved, you may want to use a Dockerfile to generate the gif to ensure reproducability (or if wish to make sure your environment variables aren't visible during the debugging session). Here is a sample Dockerfile you can modify to your liking:
+```{.Dockerfile .copy}
+# https://github.com/charmbracelet/vhs
+FROM ghcr.io/charmbracelet/vhs
+
+# Install pwndbg
+RUN apt update && apt install -y git \
+    && git clone https://github.com/pwndbg/pwndbg.git /pwndbg \
+    && cd /pwndbg \
+    && ./setup.sh
+
+# Make sure uv.lock.hash is created so we don't get
+# a message about updating during the gif.
+RUN gdb /bin/sh --batch
+
+# The ENTRYPOINT and CMD are defined in the vhs docker image.
+```
+you can use a script like this to run it easily.
+```{.bash .copy}
+#!/bin/sh
+
+set -e
+
+IMAGE_NAME="vhs-pwndbg"
+
+rm -f .gdb_history
+docker build -t "$IMAGE_NAME" .
+docker run --rm -v "$(pwd)":/vhs "$IMAGE_NAME" my_thingy.tape
+```