[Good First Issues]: update connector doc "connectors/sink-slack" - 1 point

[JieDing]

Motivation

Vanus Connect allows you to skip the complex integration with external services by offering out-of-the-box connectors.

Reviewing Vanus connector docs will be a good start if you decide to know more about Vanus Connect.

Details

Update the improper image sources in the documentation of sink-slack.

How to change

1. Fork the vanus-connect repository.
2. Create a branch update-sink-slack
3. Update file connectors/sink-slack/README.md
4. Change image source https://github.com/linkall-labs/vance/blob/main/connectors/sink-slack/message.png to https://github.com/linkall-labs/vance/blob/main/connectors/sink-slack/message.png?raw=true.
5. Submit your PR

Contribution points

Each issue counts specific points based on its difficulty. Contributors earn the corresponding points if they solve that issue. Contribution points are used to describe the contributions contributors have made. They can also be used to get rewards when there are community events.

This issue counts 1 point.

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I'd like to solve the issue, please assign it to me.

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[mendesbarreto]

@JieDing I want to solve this issue, I opened a PR already and referenced the issue on it.