Parsing of SVG files with CSS styling, FPDF.rect() with round_corners, FPDF.star()

Added

• a new option align="X" to .cell() and .multi_cell() allows to center text around the current x position, thanks to @gmischler
• allowing to provide an AnnotationName and AnnotationFlags onto text_annotation()
• allowing correctly parsing of SVG files with CSS styling (style="..." attribute), thanks to @RedShy
• FPDF.star(): new method added to draw regular stars, thanks to @digidigital and @RedShy
• FPDF.ink_annotation(): new method added to add path annotations
• allowing embedding of indexed PNG images without converting them to RGB colorspace, thanks to @RedShy
• allowing to change appearance of highlight annotations by specifying a TextMarkupType
• documentation on how to control objects transparency: link to docs
• documentation on how to create tables and charts using pandas DataFrames: link to docs, thanks to @iwayankurniawan
• added argument round_corners to FPDF.rect() that allows to draw rectangles with round corners: link to docs - thanks to @gonzalobarbaran

Fixed

• support for "x" & "y" attributes in SVG <use> tags - cf. #446
• CreationDate of PDFs generated, that was broken - cf. #451
• multi_cell() and write() ignored a trailing newline character in the supplied text since 2.5.1 - fixed thanks to @gmischler