[ZEPPELIN-3317] Update personalized mode document page

> What is this PR for?

This PR is to populate the "Personalized Mode" portion of the project that is previously devoid of any information whatsoever.
> What type of PR is it?

This would be initial Documentation for this repo

> What is the Jira issue?

>    Open an issue on Jira https://issues.apache.org/jira/browse/ZEPPELIN/

[ZEPPELIN-3317](https://issues.apache.org/jira/browse/ZEPPELIN-3317)

> How should this be tested?

No testing needed.

>    Strongly recommended: add automated unit tests for any new or changed behavior
Not needed- this is initial documentation

>     Outline any manual steps to test the PR here.

There are not steps- this is initial documentation.

> Screenshots (if appropriate)

N/A

Questions:

>     Does the license files need to update?
No license update needed.

>     Is there breaking changes for older versions?
All previous versions are blank. No breaking would occur.
>     Does this needs documentation?
This is the said documentation

Closes apache#4821 from chuckn408/master.

Signed-off-by: Cheng Pan <[email protected]>

docs/usage/other_features/personalized_mode.md

@@ -21,5 +21,12 @@ limitations under the License.
 
 # What is Personalized Mode? 
 
+Personalize your analysis result by switching the note to Personal Mode.
+
+This enables two different users to change the view of the same paragraph's result with different view even owner change paragraph and run it again.
+
+Currently, this feature is experimental. If you find any issues, please report them in 
+[Apache Zeppelin JIRA](https://issues.apache.org/jira/browse/ZEPPELIN)
+
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