Introduce MkDocs dependencies to optional `docs` group (#433)

pyproject.toml

@@ -30,6 +30,15 @@ pytest-clarity = "^1.0.1"
 [tool.poetry.extras]
 deathreaper = ["pydiscourse"]
 
+[tool.poetry.group.docs]
+optional = true
+
+[tool.poetry.group.docs.dependencies]
+mkdocs-material = "^9.5.49"
+mike = "^2.1.3"
+mkdocs-coverage = "^1.1.0"
+mkdocs-gitlab-plugin = "^0.1.4"
+
 [tool.poetry.scripts]
 silkaj = "silkaj.cli:cli"