Add discord dep

[astariul]

🔍️ Description

Note that adding this dependency is not necessary, because the code in discord_interactive package doesn't use discord.py directly.

However it is dependent on it, so if there is a breaking change in discord.py, most likely discord_interactive will not work as a result. For this reason, I'm adding discord.py as a direct dependency of discord_interactive, I believe it will make it easier to manage dependencies and versions.

🧐 Context

After major release of discord.py, the example code in this repository would (seemingly randomly) stop working. By fixing the dependency to a fixed version, we ensure it works for this version, and ensure we need to test newly released version of discord.py.

⚠️ Side-effects / Shortcomings

✅ How this was tested ?

🌱 Checklist

• Perform self-review of my own code
• Comment the code, particularly in hard-to-understand areas
• Update the documentation accordingly to the new code
• Lint / format the code