Structure policy package docs into main operator folder

Author: rdimaio

docs/operator/policy_packages/_category_.json

@@ -0,0 +1,6 @@
+{
+    "label": "Policy Packages",
+    "collapsible": true,
+    "link": {"type": "doc", "id":"operator/policy_packages/policy_packages_overview"},
+    "position": 3
+}

docs/operator_policy_packages/policy_package_algorithms.md renamed to docs/operator/policy_packages/policy_package_algorithms.md

@@ -127,7 +127,7 @@ In all cases the names used to register the functions (e.g. `voname_extract_scop
 with the name of the virtual organisation that owns the policy package,
 to avoid naming conflicts on multi-VO Rucio installations.
 
-See [the Algorithms documentation page](operator_policy_packages/policy_package_algorithms.md) for more on developing algorithms.
+See [the Algorithms documentation page](operator/policy_packages/policy_package_algorithms.md) for more on developing algorithms.
 
 ### Permission and schema modules