Add release note for 2.5.0 (opensearch-project#95)

* add release-notes folder and 2.4.0 md file

Signed-off-by: Mingshi Liu <mingshl@amazon.com>

* Add release notes for 2.5.0

Signed-off-by: Mingshi Liu <mingshl@amazon.com>

* add pr#95

Signed-off-by: Mingshi Liu <mingshl@amazon.com>

* Organized labels

Signed-off-by: Mingshi Liu <mingshl@amazon.com>

* format

Signed-off-by: Mingshi Liu <mingshl@amazon.com>

Signed-off-by: Mingshi Liu <mingshl@amazon.com>

Modifying logic to generate passages from search result document (ope…

…nsearch-project#33)

Signed-off-by: Mahita Mahesh <mahitam@amazon.com>

Change plugin name and depend on 2.4

As we get closer to releasing this plugin to work with 2.4, we should
update the name -- going with search-processor -- to better reflect the
idea that it will be able to transform search requests and responses.
Also, we need to update the build to point to 2.4 snapshots, instead of
2.1.

Signed-off-by: Michael Froh <froh@amazon.com>