Bug fix: render buttons in Live Preview mode when Obsidian starts

[Lx]

Thank you for your efforts on the Obsidian Buttons plugin.

This pull request addresses an issue where buttons would not display in Live Preview immediately after Obsidian starts, due to the "active view" not being fully initialised before Markdown processing commences.

I appreciate that you're working on a new version of Buttons but I think this fix might benefit others in the meantime if you would be willing to release it.