[README.md] Add libxml2-dev to list of dependencies

Author: Ivan Petrunko

README.md

@@ -3,7 +3,7 @@ XEP-0363: HTTP File Upload plugin for libpurple (Pidgin, Finch, etc.)
 
 ## Installation
 ### Linux, macOS
-1. Install the dependencies (`libpurple-dev`, `libglib2.0-dev`, `libgio2.0-dev`)
+1. Install the dependencies (`libxml2-dev`, `libpurple-dev`, `libglib2.0-dev`, `libgio2.0-dev`)
 2. `git clone https://github.com/Junker/purple-xmpp-http-upload.git`
 3. `cd purple-xmpp-http-upload`
 4. `make`