add simple pattern tokenizer docs

_analyzers/tokenizers/simple-pattern.md

@@ -0,0 +1,89 @@
+---
+layout: default
+title: Simple pattern
+parent: Tokenizers
+nav_order: 110
+---
+
+# Simple pattern tokenizer
+
+The `simple_pattern` tokenizer identifies matching sequences in text based on a regular expression and uses those sequences as tokens. It extracts terms that match the regular expression. Use this tokenizer when you want to directly extract specific patterns as terms.
+
+## Example usage
+
+The following example request creates a new index named `my_index` and configures an analyzer with a `simple_pattern` tokenizer. The tokenizer extracts numeric terms from text:
+
+```json
+PUT /my_index
+{
+  "settings": {
+    "analysis": {
+      "tokenizer": {
+        "my_pattern_tokenizer": {
+          "type": "simple_pattern",
+          "pattern": "\\d+"
+        }
+      },
+      "analyzer": {
+        "my_pattern_analyzer": {
+          "type": "custom",
+          "tokenizer": "my_pattern_tokenizer"
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my_index/_analyze
+{
+  "analyzer": "my_pattern_analyzer",
+  "text": "OpenSearch-2024-10-09"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "2024",
+      "start_offset": 11,
+      "end_offset": 15,
+      "type": "word",
+      "position": 0
+    },
+    {
+      "token": "10",
+      "start_offset": 16,
+      "end_offset": 18,
+      "type": "word",
+      "position": 1
+    },
+    {
+      "token": "09",
+      "start_offset": 19,
+      "end_offset": 21,
+      "type": "word",
+      "position": 2
+    }
+  ]
+}
+```
+
+## Parameters
+
+The `simple_pattern` tokenizer can be configured with the following parameter.
+
+Parameter | Required/Optional | Data type | Description
+:--- | :--- | :--- | :--- 
+`pattern` | Optional | String | The pattern used to split text into tokens, specified using a [Lucene regular expression](https://lucene.apache.org/core/9_10_0/core/org/apache/lucene/util/automaton/RegExp.html). Default is an empty string, which returns the input text as one token. 
+