build: use a src layout

[onerandomusername]

This is a feeler PR to run CI.

Testing feasibility of #1360

[read-the-docs-community]

Documentation build overview

📚 disnake | 🛠️ Build #30374621 | 📁 Comparing 62870b0 against latest (603e5c8)

🔍 Preview build

Show files changed (47 files in total): 📝 47 modified | ➕ 0 added | ➖ 0 deleted

File	Status
index.html	📝 modified
api/abc.html	📝 modified
api/activities.html	📝 modified
api/app_commands.html	📝 modified
api/app_info.html	📝 modified
api/audit_logs.html	📝 modified
api/automod.html	📝 modified
api/channels.html	📝 modified
api/clients.html	📝 modified
api/components.html	📝 modified
api/emoji.html	📝 modified
api/entitlements.html	📝 modified
api/events.html	📝 modified
api/exceptions.html	📝 modified
api/guild_scheduled_events.html	📝 modified
api/guilds.html	📝 modified
api/integrations.html	📝 modified
api/interactions.html	📝 modified
api/invites.html	📝 modified
api/localization.html	📝 modified
api/members.html	📝 modified
api/messages.html	📝 modified
api/misc.html	📝 modified
api/permissions.html	📝 modified
api/roles.html	📝 modified
api/skus.html	📝 modified
api/soundboard.html	📝 modified
api/stage_instances.html	📝 modified
api/stickers.html	📝 modified
api/subscriptions.html	📝 modified
api/ui.html	📝 modified
api/users.html	📝 modified
api/utilities.html	📝 modified
api/voice.html	📝 modified
api/webhooks.html	📝 modified
api/widgets.html	📝 modified
ext/tasks/index.html	📝 modified
ext/commands/api/app_commands.html	📝 modified
ext/commands/api/bots.html	📝 modified
ext/commands/api/checks.html	📝 modified
ext/commands/api/cogs.html	📝 modified
ext/commands/api/context.html	📝 modified
ext/commands/api/converters.html	📝 modified
ext/commands/api/exceptions.html	📝 modified
ext/commands/api/help_commands.html	📝 modified
ext/commands/api/misc.html	📝 modified
ext/commands/api/prefix_commands.html	📝 modified

[onerandomusername]

This is intended to be added but will cause a bunch of merge conflicts, so timing matters.