Source Han Serif: The second Pan-CJK typeface family from Adobe

This is Source Han Serif (JP), which supports all four variants in this family
but prioritizes Japanese Kanji over other three.

"Source Han Serif supports four different East Asian languages---Simplified
Chinese, Traditional Chinese, Japanese, and Korean---and the 65,535 glyphs in
each of its seven weights are designed to work together with a consistent design
that emphasizes shared elements between the languages while honoring the
diversity of each. Also included is a rich set of Western glyphs supporting the
Latin, Greek, and Cyrillic scripts, which were derived from Source Serif."

• The Typekit, Adobe

WWW: https://github.com/adobe-fonts/source-han-serif

PR: 232190
Submitted by: Hyun Hwang
Approved by: (one of the mentors)

• poudriere (11.2-, 12.0-RELEASE, 13.0-CURRENT@r344112 amd64 + i386) with options FULL/SUBSET each -> OK
• portlint -> OK
• Runtime tests by using desktuils/gucharmap -> OK

Minor changes from the original patch:

• Simplify the usage of the options and thus omit the bsd.port.options.mk include
• Removed variables FONTTYPE and FONTFORMAT (I haven't found any occurences of those variables in the ports framework)
• Implicit introducion of variable SRCFONTSDIR that is used by the options