Add Loading indicator when a task is created and marked as complete

[HaripriyaB]

Is your feature request related to a problem? Please describe.
Yes.

1. When a user creates a task, after clicking create button, there is a delay of 1-2 seconds for a response from the app which is not user-freindly.
2. Similar situation when a user marks a task as completed it stands still for 2sec.

Describe the solution you'd like
When a user creates a task, it has to show a loading indicator.
Similarly when a user checks the task item as completed it has to show a loading indicator.

Additional context
Current version of Task created:

Current version of Task marked as complete:

[techno-disaster]

A similar issue had been already submitted (#67) and the PR for it is already up (#83) . Will merge changes for this PR in that.