Fixes #234: Add UTF-8 charset meta tag to HTML head in visualization output

[codexvn]

Due to regional settings of the operating system, if the tag does not specify the charset, the browser may default to a non-UTF-8 encoding, resulting in garbled text.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[github-actions]

No linked issues found. Please link an issue in your pull request description or title.

Per our Contributing Guidelines, all PRs must:

• Reference an issue with one of:
  • Closing keywords: Fixes #123, Closes #123, Resolves #123 (auto-closes on merge in the same repository)
  • Reference keywords: Related to #123, Refs #123, Part of #123, See #123 (links without closing)
• The linked issue should have 5+ 👍 reactions from unique users (excluding bots and the PR author)
• Include discussion demonstrating the importance of the change

You can also use cross-repo references like owner/repo#123 or full URLs.

[github-actions]

⚠️ Branch Update Required

Your branch is 1 commits behind main. Please update your branch to ensure CI checks run with the latest code:

git fetch origin main
git merge origin/main
git push

Note: Enable "Allow edits by maintainers" to allow automatic updates.

[github-actions]

⚠️ Branch Update Required

Your branch is 3 commits behind main. Please update your branch to ensure CI checks run with the latest code:

git fetch origin main
git merge origin/main
git push

Note: Enable "Allow edits by maintainers" to allow automatic updates.

[github-actions]

⚠️ Branch Update Required

Your branch is 4 commits behind main. Please update your branch to ensure CI checks run with the latest code:

git fetch origin main
git merge origin/main
git push

Note: Enable "Allow edits by maintainers" to allow automatic updates.

[github-actions]

⚠️ Branch Update Required

Your branch is 5 commits behind main. Please update your branch to ensure CI checks run with the latest code:

git fetch origin main
git merge origin/main
git push

Note: Enable "Allow edits by maintainers" to allow automatic updates.

[github-actions]

⚠️ Branch Update Required

Your branch is 5 commits behind main. Please update your branch to ensure CI checks run with the latest code:

git fetch origin main
git merge origin/main
git push

Note: Enable "Allow edits by maintainers" to allow automatic updates.