Doc review

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>

_analyzers/tokenizers/index.md

@@ -2,7 +2,7 @@
 layout: default
 title: Tokenizers
 nav_order: 60
-has_children: false
+has_children: true
 has_toc: false
 redirect_from:
     - /analyzers/tokenizers/index/

_analyzers/tokenizers/letter.md

@@ -0,0 +1,97 @@
+---
+layout: default
+title: Letter
+parent: Tokenizers
+nav_order: 60
+---
+
+# Letter tokenizer
+
+The `letter` tokenizer splits text into words on any non-letter characters. It works well for many European languages but struggles with some Asian languages where words aren't separated by spaces.
+
+## Example usage
+
+The following example request creates a new index named `my_index` and configures an analyzer with a `letter` tokenizer:
+
+```json
+PUT /my_index
+{
+  "settings": {
+    "analysis": {
+      "analyzer": {
+        "my_letter_analyzer": {
+          "type": "custom",
+          "tokenizer": "letter"
+        }
+      }
+    }
+  },
+  "mappings": {
+    "properties": {
+      "content": {
+        "type": "text",
+        "analyzer": "my_letter_analyzer"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST _analyze
+{
+  "tokenizer": "letter",
+  "text": "Cats 4EVER love chasing butterflies!"
+}
+
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "Cats",
+      "start_offset": 0,
+      "end_offset": 4,
+      "type": "word",
+      "position": 0
+    },
+    {
+      "token": "EVER",
+      "start_offset": 6,
+      "end_offset": 10,
+      "type": "word",
+      "position": 1
+    },
+    {
+      "token": "love",
+      "start_offset": 11,
+      "end_offset": 15,
+      "type": "word",
+      "position": 2
+    },
+    {
+      "token": "chasing",
+      "start_offset": 16,
+      "end_offset": 23,
+      "type": "word",
+      "position": 3
+    },
+    {
+      "token": "butterflies",
+      "start_offset": 24,
+      "end_offset": 35,
+      "type": "word",
+      "position": 4
+    }
+  ]
+}
+```