Move docs dependency group

[CoderJoshDK]

Summary

docs is not an extra so much as it is a dev group

What is the feature request for?

The core library

The Problem

In the pyproject file, docs is under [project.optional-dependencies] when it should be under [dependency-groups]. No one should be adding disnake as a dependency with the docs extrta.

The Ideal Solution

diff --git a/pyproject.toml b/pyproject.toml
index e2d5add4..6af82b63 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,16 +53,6 @@ voice = [
     "PyNaCl>=1.5.0,<1.6",
     'audioop-lts>=0.2.1; python_version >= "3.13"'
 ]
-docs = [
-    "sphinx==7.0.1",
-    "sphinxcontrib-trio~=1.1.2",
-    "sphinx-hoverxref==1.3.0",
-    "sphinx-autobuild~=2021.3",
-    "sphinxcontrib-towncrier==0.3.2a0",
-    "towncrier==23.6.0",
-    "sphinx-notfound-page==0.8.3",
-    "sphinxext-opengraph==0.9.1",
-]

 [dependency-groups]
 dev   = [
@@ -72,6 +62,7 @@ dev   = [
     { include-group = "typing" },
     { include-group = "test" },
     { include-group = "build" },
+    { include-group = "docs" },
 ]
 nox = [
     # note: nox should be synced with nox.needs_version in noxfile.py
@@ -113,6 +104,16 @@ build = [
     "build>=1.2.2.post1",
     "twine>=6.1.0",
 ]
+docs = [
+    "sphinx==7.0.1",
+    "sphinxcontrib-trio~=1.1.2",
+    "sphinx-hoverxref==1.3.0",
+    "sphinx-autobuild~=2021.3",
+    "sphinxcontrib-towncrier==0.3.2a0",
+    "towncrier==23.6.0",
+    "sphinx-notfound-page==0.8.3",
+    "sphinxext-opengraph==0.9.1",
+]

The Current Solution

No response

Additional Context

Assuming you agree, I can make this PR. Just let me know.

[CoderJoshDK]

#1325 seems to do this. But that PR is doing a bit more. So this change can be made as its own PR.

[onerandomusername]

Thank you for this report, I've gone ahead and assigned this to you.