💡 succeed in generating pdf

I have modified codes to generate pdf file correctly.

main changes are:

• Use xelatex as the engine
• Add sphinx.ext.imgconverter to use svg file

and others.

closes #1469 (closed)

Checklist

• I am familiar with ASE's contribution guidelines.
• Doc strings in code changed in this MR are up to date.
• Unit tests have been added for new or changed code.
• Issue is resolved via "closes #XXXX" if applicable.