Added instructions to launch frontend server when running from source

[EnGassa]

When running the AutoGen Studio from source, one needs to separately launch the frontend server. Updated the docs to include these instructions.

Why are these changes needed?

The documentation for AutoGen Studio for running from source was missing the step to explicitly launch the frontend server.

Related issue number

N/A

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[realbrodiwhite]

very good

[gitguardian]

⚠️ GitGuardian has uncovered 8 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

Since your pull request originates from a forked repository, GitGuardian is not able to associate the secrets uncovered with secret incidents on your GitGuardian dashboard.
Skipping this check run and merging your pull request will create secret incidents on your GitGuardian dashboard.

🔎 Detected hardcoded secrets in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
12853598	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
10404693	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
12853599	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
10404694	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
12853601	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
10404696	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
10422482	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret
12853602	Triggered	Generic High Entropy Secret	927e788	test/oai/test_utils.py	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secrets safely. Learn here the best practices.
3. Revoke and rotate these secrets.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}