[lib] Introduce `messageStoreOperations` for `sendTextMessageActionType.started` and `sendMultimediaMessageActionTypes.started` actions in `reduceMessageStore`
[lib] Introduce `messageStoreOperations` for `sendTextMessageActionType.started` and `sendMultimediaMessageActionTypes.started` actions in `reduceMessageStore`

Summary:
Currently just creating list of ops and placing invariant

`reduceMessageStore` will be modified in a subsequent diff to include `messageStoreOperations` in its return object

Test Plan: na

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: palys-swm, Adrian, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D1858

Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal