PDF encryption - skewing - markdown hyperlinks - Python 3.11

Added

• support for PDF encryption (RC4 and AES-128): documentation page - thanks to @andersonhc
• FPDF.skew() - New method: documentation page - thanks to @erap129
• ensured support for Python 3.11
• FPDF.image(): the x parameter now accepts a value of "C" / Align.C / "R" / Align.R to horizontally position the image centered or aligned right
• FPDF.image(): dimensions can now be provided to set the intrinsic image width & height before storing it in the PDF
• FPDF.cell() & FPDF.multi_cell(): support for []() hyperlinks when markdown=True
• FPDF.write_html(): support for line-height attribute of paragraph (<p>) - thanks to @Bubbu0129
• documentation on useful tools to manipulate PDFs
• show a warning if the font being used doesn't have all the necessary glyphs for the text

Changed

• FPDF.add_link() creates a link to the current page by default, and now accepts optional parameters: x, y, page & zoom.
  Hence calling set_link() is not needed anymore after creating a link with add_link().
• FPDF.write_html() now generates warnings for unclosed HTML tags, unless warn_on_tags_not_matching=False is set

Fixed

• FPDF.write_html(): a ValueError: Incoherent hierarchy could be raised with some headings hierarchy
• FPDF.write_html(): <img> without height attribute overlaps with the following content #632 - thanks to @Bubbu0129
• FPDF.image(): performance issue with adding large images with FlateDecode image filter #644 - thanks to @Markovvn1
• FPDF.add_font(): fix support for upper case font file name #638 - thanks to @CY-Qiu