feat: add requirements.docs.txt

docs/requirements.txt

@@ -1 +0,0 @@
-esp-docs~=1.1.0

tools/requirements.json

@@ -18,6 +18,12 @@
             "description": "Packages for CI with pytest",
             "optional": true,
             "requirement_path": "tools/requirements/requirements.pytest.txt"
+        },
+        {
+            "name": "docs",
+            "description": "Packages for building ESP-IDF documentation",
+            "optional": true,
+            "requirement_path": "tools/requirements/requirements.docs.txt"
         }
     ]
 }

tools/requirements/requirements.docs.txt

@@ -0,0 +1,4 @@
+# Python package requirements for building the documentation of ESP-IDF.
+# This feature can be enabled by running "install.{sh,bat,ps1,fish} --enable-docs"
+
+esp-docs