Added information about Canvas and Campaign in Smartling descrioption

[dimitrystd]

Why are you making this change? (required)

Smartling updated its integration by addition localization support for new asset types.

Related PRs, issues, or features (optional)

This update is related to the new Translation endpoints

Feature release date (optional)

• N/A

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[lydia-xie]

Applying some edits to align with our style guide

[lydia-xie]

Closing this PR, the edits are captured in this PR. Let me know if you have any questions, thanks for submitting this! 👍