Update .nuspec

DryWetMidi/Melanchall.DryWetMidi.nuspec

@@ -17,6 +17,7 @@ DryWetMIDI is the .NET library to work with MIDI files. It allows:
 * Finely adjust process of reading and writing. It allows, for example, to read corrupted files and repair them, or build MIDI file validators.
 * Implement custom meta events and custom chunks that can be write to and read from MIDI files.
 * Easily catch specific error when reading or writing MIDI file since all possible errors in a MIDI file are presented as separate exception classes.
+* Manage content of a MIDI file either with low-level objects, like event, or high-level ones, like note.
     </description>
     <summary>.NET library to work with MIDI files</summary>
     <copyright>Copyright © Melanchall 2017</copyright>