[Cin]Website: link to html manual

I wanted to point out that, in the Support --> Documentation section of the website, the “HTML User Manual” link leads to a PDF file rather than HTML. The correct link is: https://download.cinelerra-gg.org/view.php?file=CinelerraGG_Manual/cin-index... This is just a minor detail, because clicking on “Source code” takes us to a collection of links, including one to the HTML manual.