Support ZSDCH

AG should support [~~SDCH~~](https://engineering.linkedin.com/shared-dictionary-compression-http-linkedin)/[ZSDCH](https://learn.microsoft.com/en-us/deployedge/learnmore-zsdch-compression). I've just now seen an experimental flag to turn this on in Android Edge, looked it up, & found that Chrome has been using this for almost a _decade_ (per the headers @ https://github.com/AdguardTeam/AdguardForAndroid/issues/264#issuecomment-170892197).