Simplify example folder structure (#106)

Examples are intended to be single files or modules at best, not
separate "crate-like" directories with a `src/` subdirectory yet without
`Cargo.toml`.  Not only is this [package layout documented], it also
removes the need for a specific `path =` setup as `cargo` is now able to
relate the `name` of every `[[example]]` to a specific file or directory
(`examples/<name>.rs` or `examples/<name>/main.rs`).

[package layout documented]: https://doc.rust-lang.org/cargo/guide/project-layout.html

Author: MarijnS95

Cargo.toml

@@ -55,27 +55,22 @@ features = [
 
 [[example]]
 name = "vulkan-buffer"
-path = "examples/vulkan-buffer/src/main.rs"
 required-features = ["vulkan", "ash/loaded"]
 
 [[example]]
 name = "vulkan-visualization"
-path = "examples/vulkan-visualization/src/main.rs"
 required-features = ["vulkan", "ash/loaded", "visualizer"]
 
 [[example]]
 name = "d3d12-buffer"
-path = "examples/d3d12-buffer/src/main.rs"
 required-features = ["d3d12", "public-winapi"]
 
 [[example]]
 name = "d3d12-buffer-winrs"
-path = "examples/d3d12-buffer-winrs/src/main.rs"
 required-features = ["d3d12"]
 
 [[example]]
 name = "d3d12-visualization"
-path = "examples/d3d12-visualization/src/main.rs"
 required-features = ["d3d12", "public-winapi", "visualizer"]