correct datum project import examples (#1210)

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### Summary
1. Correct documents to use correctly use 'datum project import'
command.
2. Add filtering example to filter out items containing annotations
only. (#1208)
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Resolves #111 and #222.
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- [ ] I have added integration tests to cover my changes.​
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[documentation](https://github.com/openvinotoolkit/datumaro/tree/develop/docs)
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CHANGELOG.md

@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   (<https://github.com/openvinotoolkit/datumaro/pull/1195>)
 - Fix wrong command to install datumaro from github
   (<https://github.com/openvinotoolkit/datumaro/pull/1202>, <https://github.com/openvinotoolkit/datumaro/pull/1207>)
+- Update document to correct wrong `datum project import` command and add filtering example to filter out items containing annotations.
+  (<https://github.com/openvinotoolkit/datumaro/pull/1210>)
 
 ## 16/11/2023 - Release 1.5.1
 ### Enhancements

docs/source/docs/command-reference/context_free/filter.md

@@ -126,8 +126,14 @@ Example:
   Use data only from the "s1" source of the project
   ```console
   datum project create
-  datum project import --format voc -i <path/to/dataset1/> --name s1
-  datum project import --format voc -i <path/to/dataset2/> --name s2
+  datum project import --name s1 --format voc <path/to/dataset1/>
+  datum project import --name s2 --format voc <path/to/dataset2/>
   datum filter s1 \
     -m i+a -e '/item/annotation[occluded="False"]'
   ```
+
+- Extract a dataset composed solely of items containing annotations.
+  ```console
+  datum filter -e '/item[annotation]'
+  ```
+  The `item[annotation]` checks if there is a child named `annotation` within the `item` node.

docs/source/docs/data-formats/formats/sly_pointcloud.md

@@ -57,13 +57,8 @@ Point Cloud dataset directory should have the following structure:
     └── meta.json
 ```
 
-There are two ways to import a Supervisely Point Cloud dataset:
+Use the command below to import a Supervisely Point Cloud dataset:
 
-```bash
-datum project create
-datum project import --format sly_pointcloud --input-path <path/to/dataset>
-```
-or
 ``` bash
 datum project create
 datum project import -f sly_pointcloud <path/to/dataset>