first dictionary for spellcheck.py

doc/src/sketcher/dictionary.txt

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+ImageMagick
+Informatics
+Langtangen
+Matplotlib
+OO
+Pysketcher
+SciTools
+Simula
+anim
+befined
+bicyle
+botton
+ch
+classname
+com
+demystify
+dt
+ffmpeg
+fillcolor
+gif
+github
+graphviz
+hier
+hplgit
+html
+http
+img
+linecolor
+linestyle
+linetype
+linewidth
+org
+png
+py
+pysketcher
+src
+subdictionaries
+subfigures
+tmp
+txt
+vectorized