add string.split processor

src/content/docs/processors/string/split.md

@@ -0,0 +1,18 @@
+---
+title: String Split
+sidebar:
+    order: 5
+---
+The `string.split` processor takes a string and turns it into an array of strings by splitting on `params.separator`. This processor will return an error if the message being processed is not a string.
+
+- **type**: `string.split`
+- **params**:
+    - **pattern**: string to split incoming string on
+
+### Example
+Split incoming string on `,` i.e `"one,two,three"` -> `["one","two","three"]`
+```
+- type: string.split
+  params:
+    separator: ","
+```