add follow method: local or global

[yuchen-lea]

Since I have 1w+ nodes, follow emacs in a global graph is low performance and not very useful.

I add a new variable org-roam-ui-follow-method.

If this is set to global, it behaves like before;
If this is set to local, it will auto open the corresponding local graph of current node.

[tefkah]

Thanks for the PR! While I like being able to configure this in Emacs, this behavior is already configurable in org-roam-ui (go to behavior and then to "Follow Emacs by..."), and changing this behavior in Emacs would not automatically change what that option does (it wouldn't do anything). Does that option work for you?

We plan to have all of the options in the UI configurable in Emacs anyway, so I feel like having this specific option toggleable in Emacs at this time will lead to confusion down the road, as we would either have to remove it or have it be separate to the rest of the configuration, neither of which sound ideal to me. What do you think?

Also, thanks for spotting the typo!