add docs for db and redis

src/content/docs/processors/kv/set.md

@@ -0,0 +1,22 @@
+---
+title: Set
+sidebar:
+    order: 2
+---
+The `kv.set` processor sets the value associated with a key from a compatible module. The payload is unchanged so whatever is received by this payload is output unless any errors are encountered.
+
+- **type**: `kv.set`
+- **params**:
+    - **module**: id of the module
+    - **key**: the key to look up
+    - **value**: the value to set
+
+### Example
+This will attempt to set the key `hello` to `world` using the module with an id of `redis`
+```
+- type: kv.set
+  params:
+    module: redis
+    key: hello
+    value: world
+```