libopus bindings

It is a simple binding and safe abstraction over libopus.

Building

To build the code, always have a look at CI to install the necessary dependencies on all
supported operating systems.

Building with vcpkg for Windows x64

To build with vcpkg, you need to follow these
steps:

Install pkg-config through chocolatey
```
choco install pkgconfiglite
```
Install opus
```
vcpkg install opus:x64-windows
```
Add to the PKG_CONFIG_PATH environment variable the path $VCPKG_INSTALLATION_ROOT\installed\x64-windows\lib\pkgconfig
Build code
```
cargo build --workspace
```

To speed up the computation, you can build your packages only in Release mode
adding the set(VCPKG_BUILD_TYPE release) line to the
$VCPKG_INSTALLATION_ROOT\triplets\x64-windows.cmake file.

Building for Windows x86 is the same, just replace x64 with x86 in the
steps above.

TODO

Simple bindings
Safe abstraction
Examples