feat(plot): the figure crosshair marks the hovered row, and the stroke is thin, dashed and configurable

src/render/program.cpp

@@ -23,6 +23,10 @@ void LineProgram::set_viewport(Vec2 px) const noexcept { program_.set_uniform("u
 
 void LineProgram::set_width(f32 px) const noexcept { program_.set_uniform("u_width", px); }
 
+void LineProgram::set_dash(Vec2 on_off) const noexcept {
+  program_.set_uniform("u_dash", on_off);
+}
+
 void LineProgram::set_color(Color color) const noexcept { program_.set_uniform("u_color", color); }
 
 bool TextProgram::create(Status* st) noexcept {