allows passing of custom storage and introduces sdk modes

[arch1995]

Motivation and Context

We want to remove extra deps for react native and nodejs backend. Hence we allow sfa web to accept various new params like mode and storage to customise sdk usage.

Jira Link: https://toruslabs.atlassian.net/browse/PD-4010

Description

• Accept two new params in the constructor - mode, and storage.
• Defines a async storage to save sfa data.

How has this been tested?

Developer and devrels tested this.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project. (run lint)
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[chaitanyapotti]

lgtm

[yashovardhan]

Tested. All examples work as expected