Add `Smooth Pixel-perfect camera` example

[LeviLovie]

[LeviLovie]

@deltaphc I'm sorry to disturb, but I'm having problem testing if my example works here, when i try cargo run in the showcase dir it crahes:

cargo run
error: current package believes it's in a workspace when it's not:
current:   /Users/levi/Dev/UnsafeSoftware/raylib-rs/showcase/Cargo.toml
workspace: /Users/levi/Dev/UnsafeSoftware/raylib-rs/Cargo.toml

this may be fixable by adding `showcase` to the `workspace.members` array of the manifest located at: /Users/levi/Dev/UnsafeSoftware/raylib-rs/Cargo.toml
Alternatively, to keep it out of the workspace, add the package to the `workspace.exclude` array, or add an empty `[workspace]` table to the package's manifest.

[LeviLovie]

Also, I'm sorry if i did something wrong, I'm new to contributing

[IoIxD]

If you're still interested in merging this, development now happens over at raylib-rs/raylib-rs.

Also you would need to merge this into the main branch, not showcase-all