manual: Mention [lack of] unicode normalization in the manual

Change-Id: Icdb19a47367fbe7b2fd32679885a26669a799612

manual/appendix/file_formats.tex

@@ -377,4 +377,14 @@
         \item The maximum size of each metadata item (e.g. Artists) is limited
               to 90 bytes.
     }
+    \opt{utf8proc}{
+        \item All textual metadata is normalized into most compact Unicode
+              NFC form. This simplifies font/glpyh rendering, and makes
+              it possible to compare/sort strings that use different
+              normalization forms.
+    }
+    \nopt{utf8proc}{
+        \item Due to RAM limitations, the \playertype does not process or
+              normalize textual metadata in any way.
+    }
     \end{enumerate}