Update manual.md

Author: jdutant

docs/manual.md

@@ -1,8 +1,8 @@
-Imagify - Pandoc/Quarto filter to convert selected LaTeX into images
-====================================================================
+Imagify - Pandoc/Quarto conversion of LaTeX and TikZ elements into images
+=========================================================================
 
-Lua filter to convert some or all LaTeX code in a document into 
-images and to use `.tex`/`.tikz` files as image sources. 
+Lua filter to convert some or all LaTeX and TikZ elements in a document into 
+images. Also enables using `.tex`/`.tikz` files as image sources. 
 
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 [Julien Dutant][JDutant].