Add doc for nft_sell_offers method

Per TOK-57.

content/references/rippled-api/public-rippled-methods/nft-methods/nft_sell_offers.md

@@ -0,0 +1,112 @@
+---
+html: nft_sell_offers.html
+parent: nft-methods.html
+blurb: Get a list of all sell offers for a NFToken.
+labels:
+  - Non-fungible Tokens, NFTs, NFTokens
+---
+# account_nfts
+[[Source]](https://github.com/ripple/rippled/blob/xls20/src/ripple/rpc/handlers/NFTOffers.cpp "Source")
+{% include '_snippets/nfts-disclaimer.md' %}
+
+The `nft_sell_offers` method returns a list of sell offers for a `NFToken` object.
+
+## Request Format
+An example of the request format:
+
+<!-- MULTICODE_BLOCK_START -->
+
+*WebSocket*
+
+```json
+{
+   "id": 1,
+   "command": "nft_sell_offers",
+   "params": [{
+   		"tokenid": "00090000D0B007439B080E9B05BF62403911301A7B1F0CFAA048C0A200000007"
+   }]
+}
+```
+
+*JSON-RPC*
+
+```json
+{
+    "method": "nft_sell_offers",
+    "tokenid": "00090000D0B007439B080E9B05BF62403911301A7B1F0CFAA048C0A200000007"
+}
+```
+
+<!-- MULTICODE_BLOCK_END -->
+
+[Try it! >](websocket-api-tool.html#nft_sell_offers)
+
+The request includes the following parameters:
+
+| Field                 | Type                       | Description             |
+|:----------------------|:---------------------------|:------------------------|
+| `tokenid`             | String                     | The unique identifier of a NFToken object. |
+|
+## Response Format
+An example of a successful response:
+
+<!-- MULTICODE_BLOCK_START -->
+
+*WebSocket*
+
+```json
+{
+  "id": 0,
+  "result": {
+    "offers": [
+      {
+        "amount": "100",
+        "flags": 1,
+        "index": "0468126DEDD7EF3F624137F55F4BABE6BEFB4A2CE8F2D9E5D7756FD06B9B2045",
+        "owner": "rGJUF4PvVkMNxG6Bg6AKg3avhrtQyAffcm"
+      }
+    ],
+    "tokenid": "000900001FD350FC4A6133360827DE142E60E7522E4F4DF529ABA6A80000000D"
+  },
+  "type": "response"
+}
+```
+
+*JSON-RPC*
+
+```json
+{
+	{
+	  "id": 0,
+	  "result": {
+		"offers": [
+		  {
+			"amount": "100",
+			"flags": 1,
+			"index": "0468126DEDD7EF3F624137F55F4BABE6BEFB4A2CE8F2D9E5D7756FD06B9B2045",
+			"owner": "rGJUF4PvVkMNxG6Bg6AKg3avhrtQyAffcm"
+		  }
+		],
+		"tokenid": "000900001FD350FC4A6133360827DE142E60E7522E4F4DF529ABA6A80000000D"
+	  },
+	  "type": "response"
+	}
+}
+```
+
+<!-- MULTICODE_BLOCK_END -->
+
+The response follows the [standard format][], with a successful result containing the following fields:
+
+| `Field`        | Type             | Description                              |
+|:---------------|:-----------------|:-----------------------------------------|
+| `tokenid` | String | The NFToken associated with the sell offers |
+| `offers` | Array | The list of sell offers for the NFToken |
+
+## Possible Errors
+
+* Any of the [universal error types][].
+
+
+{% include '_snippets/rippled_versions.md' %}
+{% include '_snippets/rippled-api-links.md' %}