[schloerke]

Closes #76

The graph draws three kinds of edges, but the legend only explained node colors. This adds three line rows below the color rows: a solid line for a dependency, a dashed line for an isolate()d dependency, and a dotted line for an inactive dependency (one that existed earlier in the replay but is not active at the current step). The rows are plain HTML in reactlog.html with a small .legendLine CSS class; srcts/index.ts sets each line color from colors.edges / colors.ghostEdges, the same way the color boxes are set, so the legend stays in sync with cytoStyle.ts.

To verify: run npm run build, open inst/reactlog/reactlog.html through a local web server, and check the bottom-left legend shows the three line rows matching the edges on the graph.