chore: add ci tests

[fadi-george]

Description

One Line Summary

• run tests in ci workflow

Details

• adds vitest & happy-dom package and new test scripts in package json
• adds simple index test file

Motivation

• want to have more test coverage for sdk packages

Testing

Unit testing

• ran bun run test and got all tests passing
• also tested example app on emulators

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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This change is 

[nan-li]

Let's organize the testing structure. Curently there is a first-level /mocks directory and index.test.ts lives among the regular files under /www.

[nan-li]

nit: Should we include this expect for getPushSubscriptionId?

[fadi-george]

.test. next to files would help identify which files have test or not.

[fadi-george]

Otherwise youd hvea tests/ folder that looks identical e.g.
tests/
index.test.ts
DebugNamespace.test.ts
InAppMessagesNamespace.test.ts
etc.

[nan-li]

Sounds good, I searched testing structures and found this pattern is termed colocating / colocation..