Add porter stem token filter docs #8271 (#8278)

* adding porter stem token filter docs #8271

Signed-off-by: Anton Rubin <[email protected]>

* Doc review

Signed-off-by: Fanit Kolchina <[email protected]>

* Apply suggestions from code review

Co-authored-by: Nathan Bower <[email protected]>
Signed-off-by: kolchfa-aws <[email protected]>

---------

Signed-off-by: Anton Rubin <[email protected]>
Signed-off-by: Fanit Kolchina <[email protected]>
Signed-off-by: kolchfa-aws <[email protected]>
Co-authored-by: Fanit Kolchina <[email protected]>
Co-authored-by: kolchfa-aws <[email protected]>
Co-authored-by: Nathan Bower <[email protected]>
(cherry picked from commit 5e2fc78)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

_analyzers/token-filters/index.md

@@ -48,7 +48,7 @@ Token filter | Underlying Lucene token filter|  Description
 [`pattern_capture`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/pattern-capture/) | N/A | Generates a token for every capture group in the provided regular expression. Uses [Java regular expression syntax](https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html).
 [`pattern_replace`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/pattern-replace/) | N/A | Matches a pattern in the provided regular expression and replaces matching substrings. Uses [Java regular expression syntax](https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html).
 `phonetic`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/phonetic/) | N/A | Uses a phonetic encoder to emit a metaphone token for each token in the token stream. Requires installing the `analysis-phonetic` plugin.
-`porter_stem` | [PorterStemFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/en/PorterStemFilter.html) | Uses the [Porter stemming algorithm](https://tartarus.org/martin/PorterStemmer/) to perform algorithmic stemming for the English language.
+[`porter_stem`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/porter-stem/) | [PorterStemFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/en/PorterStemFilter.html) | Uses the [Porter stemming algorithm](https://tartarus.org/martin/PorterStemmer/) to perform algorithmic stemming for the English language.
 [`predicate_token_filter`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/predicate-token-filter/) | N/A | Removes tokens that do not match the specified predicate script. Supports only inline Painless scripts.
 `remove_duplicates` | [RemoveDuplicatesTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/RemoveDuplicatesTokenFilter.html) | Removes duplicate tokens that are in the same position.
 `reverse` | [ReverseStringFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/reverse/ReverseStringFilter.html) | Reverses the string corresponding to each token in the token stream. For example, the token `dog` becomes `god`.

_analyzers/token-filters/porter-stem.md

@@ -0,0 +1,83 @@
+---
+layout: default
+title: Porter stem
+parent: Token filters
+nav_order: 340
+---
+
+# Porter stem token filter
+
+The `porter_stem` token filter reduces words to their base (or _stem_) form and removes common suffixes from words, which helps in matching similar words by their root. For example, the word `running` is stemmed to `run`. This token filter is primarily used for the English language and provides stemming based on the [Porter stemming algorithm](https://snowballstem.org/algorithms/porter/stemmer.html).
+
+
+## Example
+
+The following example request creates a new index named `my_stem_index` and configures an analyzer with a `porter_stem` filter:
+
+```json
+PUT /my_stem_index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_porter_stem": {
+          "type": "porter_stem"
+        }
+      },
+      "analyzer": {
+        "porter_analyzer": {
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "my_porter_stem"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my_stem_index/_analyze
+{
+  "text": "running runners ran",
+  "analyzer": "porter_analyzer"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "run",
+      "start_offset": 0,
+      "end_offset": 7,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "runner",
+      "start_offset": 8,
+      "end_offset": 15,
+      "type": "<ALPHANUM>",
+      "position": 1
+    },
+    {
+      "token": "ran",
+      "start_offset": 16,
+      "end_offset": 19,
+      "type": "<ALPHANUM>",
+      "position": 2
+    }
+  ]
+}
+```