JS/TS bindings don't allow setting auto splitter settings

I was looking into possibly implementing LiveSplit/LiveSplitOne#459, but there appears to be no way for the autosplitter to communicate settings to LSO, since the TypeScript API only provides [read access](https://livesplit.org/livesplit-core-docs/classes/runref.html#autosplittersettings).

Start with the TypeScript API's read-only autosplitter settings access documented on RunRef, then trace how those bindings expose settings. Done means an autosplitter can communicate settings to LiveSplitOne through the JS/TS API, with the corresponding binding behavior covered by the project's existing checks.

Written by the indexing model from the issue text.