[explorer] Locate current buffer in the filetree

[LintaoAmons]

Don't know if there's a method equivalent to the Neotree reveal reveal_force_cwd to locate the current buffer in the file tree?

[folke]

Just added Snacks.explorer.reveal().
When not open yet, it will open an explorer.

IF the explorer's cwd doesn't contain the file, it will go up thr tree until it's visible and then focus it.