As mentioned in https://github.com/knsv/mermaid/issues/291#issuecomment-287673609, the
parameter should be `startOnLoad` instead of `loadOnStart`. In addition, `mermaid.initialize()`
expects to see `startOnLoad` in the `mermaid` hash:

https://github.com/knsv/mermaid/blob/6cd5ffe637d88525b93417bf3954e9c0e5a4deb8/src/mermaid.js#L118

Closes #42052