message: Update MeshBuilder.triangles
  The API method (`add_vertex`) of `BufferedBuilder` that allowed adding
  arbitrary points has been removed. The only solution I could find was to
  simply insert the vertices directly into the `VertexBuffers` without
  using `BufferedBuilder` as an abstraction.
diff: +use std::convert::TryInto;
  +
  use crate::context::DebugId;
  use crate::error::GameError;
  use crate::graphics::*;
  @@ -395,22 +397,17 @@ impl MeshBuilder {
  let vb = VertexBuilder {
  color: LinearColor::from(color),
  };
  - let builder: &mut t::BuffersBuilder<_, _, _> =
  - &mut t::BuffersBuilder::new(&mut self.buffer, vb);
  - use lyon::tessellation::BasicGeometryBuilder;
  - //builder.begin_geometry();
  for tri in tris {
  // Ideally this assert makes bounds-checks only happen once.
  assert!(tri.len() == 3);
  - let fst = tri[0];
  - let snd = tri[1];
  - let thd = tri[2];
  - let _i1 = builder.add_vertex(fst)?;
  - let _i2 = builder.add_vertex(snd)?;
  - let _i3 = builder.add_vertex(thd)?;
  - //builder.add_triangle(i1, i2, i3);
  - }
  - //let _ = builder.end_geometry();
  + let first_index: u32 = self.buffer.vertices.len().try_into().unwrap();
  + self.buffer.vertices.push(vb.new_vertex(tri[0]));
  + self.buffer.vertices.push(vb.new_vertex(tri[1]));
  + self.buffer.vertices.push(vb.new_vertex(tri[2]));
  + self.buffer.indices.push(first_index);
  + self.buffer.indices.push(first_index + 1);
  + self.buffer.indices.push(first_index + 2);
  + }
  }
  Ok(self)
  }
  