* feat(convert): support base64 encoded videos

Thanks to @t-fritsch, Manim Slides can now convert to a fully self-contained HTML presentation using base64 encoded videos!

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* chore(lib): explicit decode type

* feat(lib): auto detect mime type

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci



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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>