Font optimisation

I have done some tweaks to fonts on the site. In particular I optimised the fonts I use for headings on the homepage using the pyftsubset command in Font Tools to consist only of the characters needed to display the text used on the site and no more. This should reduce the download footprint of the site a bit.

I don’t remember who I saw link to pyftsubset originally so can’t give credit for where I saw it, unfortunately.