Improve 'set-local-storage-item' — allow modifying nested properties

Currently, only top-level keys can be modified in local storage using the `set-local-storage-item` scriptlet. However, some applications store data in local storage by saving an object and using nested properties within it.

A good example is help.semmelweis.hu, where the result of the cookie notice is stored under the `app` key in local storage, specifically within a nested object such as `app.consentOptions.analytics`.

At the moment, there’s no way to do something like this:

```adblock
help.semmelweis.hu#%#//scriptlet('set-local-storage-item', 'app.consentOptions.functional', 'true')
help.semmelweis.hu#%#//scriptlet('set-local-storage-item', 'app.consentOptions.analytics', 'false')
help.semmelweis.hu#%#//scriptlet('set-local-storage-item', 'app.consentOptions.marketing', 'false')
```

For backward compatibility, perhaps the best option would be to add a new parameter that determines whether dots should be interpreted as nesting. The default value of this parameter would be `false`. There are two main reasons for this:
- currently, both ADG and uBO include an example in their documentation using `player.live.current.mute`, and
- there are also existing matches for the regex `'?set-local-storage-item'?, '?.*\.` in both the AdGuard Filters and uAssets.