Add dynamic rooms docs (#19199)

* Add dynamic rooms docs

* fix typos, structure and wrong snippet

* simplify

---------

Co-authored-by: Fotis Voutsas <fotis@netdata.cloud>
Co-authored-by: ilyam8 <ilya@netdata.cloud>

docs/netdata-cloud/node-membership-rules.md

@@ -0,0 +1,69 @@
+# Node Membership Rules
+
+Node Membership Rules automate Node organization within Rooms based on host labels. This simplifies infrastructure management by dynamically assigning Nodes to appropriate Rooms, eliminating manual intervention.
+
+**Important**:
+
+- Rules work with all Rooms except the "All Nodes" Room, as it includes all Nodes by default.
+- Creating and editing Rules requires Node management permissions.
+- Rules are evaluated in real-time as labels change.
+- Exclusion rules always override inclusion rules.
+
+## Rule Structure
+
+The rules consist of the following elements:
+
+| Element | Description                                                                                       |
+|:--------|:--------------------------------------------------------------------------------------------------|
+| Action  | Determines whether matching Nodes will be included or excluded from the Room                      |
+| Clauses | Set of conditions that determine which Nodes match the Rule (all must be satisfied - logical AND) |
+
+Each clause consists of:
+
+| Element  | Description                  |
+|:---------|:-----------------------------|
+| Label    | The host label to check      |
+| Value    | The comparison method        |
+| Operator | The value to compare against |
+
+Below is a conceptual representation of a rule that includes all production database Nodes. The structure is shown in YAML format for clarity:
+
+```yaml
+Action: Include
+Clauses:
+  - Label: environment
+    Operator: equals
+    Value: production
+  - Label: service-type
+    Operator: equals
+    Value: database
+```
+
+## Rule Evaluation Order
+
+- Inclusion rules are checked first
+- Exclusion rules are checked second
+  If both match, exclusion wins
+
+## Creating Rules
+
+1. Access Settings
+    - Click ⚙️ (Room settings)
+    - Select "Nodes" tab
+2. Create Rule
+    - Click "Add new Rule"
+    - Select Action (Include/Exclude)
+    - Add clause(s)
+    - Save changes
+
+## Membership Status
+
+Nodes can have multiple membership types in a Room:
+
+| Status          | Description                |
+|:----------------|:---------------------------|
+| STATIC          | Manually added to the Room |
+| RULE            | Added by matching Rule(s)  |
+| STATIC and RULE | Both manual and Rule-based |
+
+You can view each Node's membership status in the Room's Nodes table under the "Membership" column.