support AdGuard scriptlet syntax

AdGuard uses `#%#//scriptlet(...)` for scriptlet injection syntax, whereas uBO filter lists generally use `+js(...)`. AdGuard's syntax requires quoting, which is supported in adblock-rust as of v0.8.3, so it could now be supported as an additional syntax alias.

Start by locating the parser and existing handling for uBO `+js(...)` scriptlet filters, then read how quoted arguments are represented since adblock-rust v0.8.3 supports them. Add the AdGuard `#%#//scriptlet(...)` form as an additional syntax alias and verify that representative quoted scriptlet filters are accepted without changing existing syntax behavior.

Written by the indexing model from the issue text.