[doc] Add Spec of Index Manifest

docs/content/concepts/spec/manifest.md

@@ -28,6 +28,11 @@ under the License.
 
 ## Manifest List
 
+```shell
+├── manifest
+    └── manifest-list-51c16f7b-421c-4bc0-80a0-17677f343358-1
+```
+
 Manifest List includes meta of several manifest files. Its name contains UUID, it is a avro file, the schema is:
 
 1. fileName: manifest file name.
@@ -40,12 +45,22 @@ Manifest List includes meta of several manifest files. Its name contains UUID, i
 
 ## Manifest
 
-Manifest includes meta of several data files or changelog files. Its name contains UUID, it is a avro file.
+Manifest includes meta of several data files or changelog files or table-index files. Its name contains UUID, it is an
+avro file.
 
 The changes of the file are saved in the manifest, and the file can be added or deleted. Manifests should be in
 an orderly manner, and the same file may be added or deleted multiple times. The last version should be read. This
 design can make commit lighter to support file deletion generated by compaction.
 
+### Data Manifest
+
+Data Manifest includes meta of several data files or changelog files.
+
+```shell
+├── manifest
+    └── manifest-6758823b-2010-4d06-aef0-3b1b597723d6-0
+```
+
 The schema is:
 
 1. kind: ADD or DELETE,
@@ -71,3 +86,28 @@ The data file meta is:
 13. creationTime: creation time of this file.
 14. deleteRowCount: rowCount = addRowCount + deleteRowCount.
 15. embeddedIndex: if data file index is too small, store the index in manifest.
+
+### Index Manifest
+
+Index Manifest includes meta of several [table-index]({{< ref "concepts/spec/tableindex" >}}) files.
+
+```shell
+├── manifest
+    └── index-manifest-5d670043-da25-4265-9a26-e31affc98039-0
+```
+
+The schema is:
+
+1. kind: ADD or DELETE,
+2. partition: partition spec, a BinaryRow.
+3. bucket: bucket of this file.
+4. indexFile: index file meta.
+
+The index file meta is:
+
+1. indexType: string, "HASH" or "DELETION_VECTORS".
+2. fileName: file name.
+3. fileSize: file size.
+4. rowCount: total number of rows.
+5. deletionVectorsRanges: Metadata only used by "DELETION_VECTORS", Stores offset and length of each data file,
+   The schema is `ARRAY<ROW<f0: STRING, f1: INT, f2: INT>>`.