Sanitize invalid XML characters in text content

Strip invalid XML 1.0 control characters (0x00-0x08, 0x0B-0x0C, 0x0E-0x1F)
from text to prevent corrupted docx files that fail to open in LibreOffice.

Fixes SAXParseException 'PCData Invalid Char value' errors.

lib/notare/nodes/run.rb

@@ -8,7 +8,7 @@ module Notare
       def initialize(text, bold: false, italic: false, underline: false,
                      strike: false, highlight: nil, color: nil, style: nil)
         super()
-        @text = text
+        @text = XmlSanitizer.sanitize(text)
         @bold = bold
         @italic = italic
         @underline = underline