Add sendwithus email provider

[scopsy]

%23%23%23 What changed%3F Why was the change needed%3F

Added Sendwithus as a new email provider. This change was needed to expand the range of supported email service providers for users, following the existing patterns for email integrations.

This includes:

• Core provider implementation (@novu/providers).
• API and worker support (@novu/application-generic).
• Dashboard UI configuration (@novu/shared).
• Unit tests for the new provider.

Relevant documentation: Sendwithus API

%23%23%23 Screenshots

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%23%23%23 Related enterprise PR

%23%23%23 Special notes for your reviewer

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[github-actions]

Hey there and thank you for opening this pull request! 👋

We require pull request titles to follow the Conventional Commits specification and it looks like your proposed title needs to be adjusted.

Your PR title is: Add sendwithus email provider
It should be something like: feat(scope): Add fancy new feature

Details:

No release type found in pull request title "Add sendwithus email provider". Add a prefix to indicate what kind of release this pull request corresponds to. For reference, see https://www.conventionalcommits.org/

Available types:

• feat: A new feature
• fix: A bug fix
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• refactor: A code change that neither fixes a bug nor adds a feature
• perf: A code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
• ci: Changes to our CI configuration files and scripts (example scopes: Travis, Circle, BrowserStack, SauceLabs)
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit