Mark geometry lane based on `placement=` tags

For his Straßenraumkarte, Supaplex uses the tag `placement=right_of:1` to clarify where lanes are positioned in relation to the geometry-line.

> Additionally, placement=right_of:1 helps to place the lanes precisely in relation to position of the osm way by indicating that the way geometry is located right of the first (left) lane and all other lanes are to be rendered right of it.

https://supaplexosm.github.io/strassenraumkarte-neukoelln/posts/2021-12-31-micromap-update#bike-lanes-position-them-right

---

I think osm2lanes would have to evaluate this tag in order to allow renderer to precisely position the lanes.

---

Maybe the osm2lanes schema could be something like this

> lane1 > position_from_geometry=-2
> lane2 > position_from_geometry=-1
> lane3 > position_from_geometry=0
> lane4 > position_from_geometry=1

---

I don't think that is the next important part, but I was thinking about it and wanted to start the documentation/discussion.