Added new examples (#1031)

* Added new examples

* Fixed examples links

docs/examples/reindex.asciidoc

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+[[reindex_examples]]
+== Reindex
+
+The `reindex` API extracts the document source from the source index and indexes the documents into the destination index. You can copy all documents to the destination index, reindex a subset of the documents or update the source before to reindex it.
+
+In the following example we have a `game-of-thrones` index which contains different quotes of various characters, we want to create a new index only for the house Stark and remove the `house` field from the document source.
+
+[source,js]
+----
+'use strict'
+
+const { Client } = require('@elastic/elasticsearch')
+const client = new Client({ node: 'http://localhost:9200' })
+
+async function run () {
+  await client.index({
+    index: 'game-of-thrones',
+    body: {
+      character: 'Ned Stark',
+      quote: 'Winter is coming.',
+      house: 'stark'
+    }
+  })
+
+  await client.index({
+    index: 'game-of-thrones',
+    body: {
+      character: 'Arya Stark',
+      quote: 'A girl is Arya Stark of Winterfell. And I\'m going home.',
+      house: 'stark'
+    }
+  })
+
+  await client.index({
+    index: 'game-of-thrones',
+    refresh: true,
+    body: {
+      character: 'Tyrion Lannister',
+      quote: 'A Lannister always pays his debts.',
+      house: 'lannister'
+    }
+  })
+
+  await client.reindex({
+    waitForCompletion: true,
+    refresh: true,
+    body: {
+      source: {
+        index: 'game-of-thrones',
+        query: {
+          match: { character: 'stark' }
+        }
+      },
+      dest: {
+        index: 'stark-index'
+      },
+      script: {
+        lang: 'painless',
+        source: 'ctx._source.remove("house")'
+      }
+    }
+  })
+
+  const { body } = await client.search({
+    index: 'stark-index',
+    body: {
+      query: { match_all: {} }
+    }
+  })
+
+  console.log(body.hits.hits)
+}
+
+run().catch(console.log)
+----