Persist display mode / subdisplay options in querystring

[jacobwegner]

Users should be able to copy the current URL and have the display mode / subdisplay options preserved (e.g, folio mode with only folios visible).

When users change to another display mode. that "subdisplay" state should reset (see discussion in #26).

[jacobwegner]

@jtauber This is ready for review via https://deploy-preview-47--sv-mini.netlify.app/reader/urn:cts:greekLit:tlg0012.tlg001.perseus-grc2:1.1-1.7

e.g. the following URL will open in metrical display mode:

https://deploy-preview-47--sv-mini.netlify.app/reader/urn:cts:greekLit:tlg0012.tlg001.perseus-grc2:1.1-1.7?mode=metrical

If you select another version from the library widget, we are currently reverting to default mode:

frontend/packages/widget-library/src/Node.vue

Line 11 in f106dd6

<ReaderLink