fix(build): add umd build for deploy step, provide local build command

[sreenara]

COMPLETES #NA

This pull request addresses

the issue of not building the bundles for deployment.

by making the following changes

1. Fixed the command to build UMD in the deploy.yml
2. Added a script in the root package.json to make it easier for developers to build locally and test samples
3. Changed the commands in the CONTRIBUTING.md accordingly.
4. Removed unnecessary webex dependency in packages/calling/package.json

Change Type

• 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 change)
• Documentation update
• Tooling change
• Internal code refactor

The following scenarios where tested

Tested building the code - UMD folder created successfully
No errors observed for commands running in deploy.yml
Was able to build and host samples page locally.

I certified that

• I have read and followed contributing guidelines

• I discussed changes with code owners prior to submitting this pull request

• I have not skipped any automated checks

• All existing and new tests passed

• I have updated the documentation accordingly

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Make sure to have followed the contributing guidelines before submitting.

[rarajes2]

Did we remove this intentionally?

[sreenara]

Yes @rarajes2 . We removed this because we don't use webex as a dependency this way. We actually never used it even while this was in the internal repo. This should have been removed long ago.