Docs: Add a dependencies section in the README (#2)

README.md

@@ -19,6 +19,29 @@ The library offers:
 ## Intents
 Songbird's gateway functionality requires you to specify the `GUILD_VOICE_STATES` intent.
 
+## Dependencies
+
+Songbird needs a few system dependencies before you can use it.
+
+- Opus - Audio codec that Discord uses.
+If you are on Windows and you are using the MSVC toolchain, a prebuilt DLL is provided for you, you do not have to do anything.
+On other platforms, you will have to install it. You can install the library with `apt install libopus-dev` on Ubuntu or `pacman -S opus` on Arch Linux.
+If you do not have it installed it will be built for you. However, you will need a C compiler and the GNU autotools installed.
+Again, these can be installed with `apt install build-essential autoconf automake libtool m4` on Ubuntu or `pacman -S base-devel` on Arch Linux.
+
+This is a required dependency. Songbird cannot work without it.
+
+- FFmpeg - Audio/Video conversion tool.
+You can install the tool with `apt install ffmpeg` on Ubuntu or `pacman -S ffmpeg` on Arch Linux.
+
+This is an optional, but recommended dependency. It allows Songbird to convert from, for instance, .mp4 files to the audio format Discord uses.
+
+- youtube-dl - Audio/Video download tool.
+You can install the tool with Python's package manager, pip, which we recommend for youtube-dl. You can do it with the command `pip install youtube_dl`.
+Alternatively, you can install it with your system's package manager, `apt install youtube-dl` on Ubuntu or `pacman -S youtube-dl` on Arch Linux.
+
+This is an optional dependency. It allows Songbird to download an audio source from the Internet, which will be converted to the audio format Discord uses.
+
 ## Examples
 Full examples showing various types of functionality and integrations can be found in [this crate's examples directory].