pdf, docx, html to text fragments

[despiegk]

best way how to convert pdf, docx, html to list of text fragments

these text fragments can then be given to vilnus see #292

requirements

• low mem footprint
• few requirements on system (don't drag in many libs, ...)
• osx,linux,windows support
• fast enough

todo

• research
• make nice SAL for it (osal)

[ashraffouda]

since we don't have tools in vlang to do this and also using any of ready to use tools will not be the same on all platforms (windows, linux and osx) I created this tool in rust which can be built and used as a binary https://github.com/ashraffouda/extractor and pr for crystallib is here https://github.com/freeflowuniverse/crystallib/pull/311