fontconfig config description

[Akira TAGOH]

Hi,

I'm adding a feature to enable/disable the fontconfig configuration files from packages for users and per-users in fonts-tweak-tool and almost has already been implemented in git. I believe this feature allows more customization around fonts.
One problem on this is, it is quite hard to see what it is for from those filenames. those might contains multiple rulesets too.

So I'd like to propose adding the description in the certain syntax to the files and the template. and according to this change I'd encourage packagers to have a separate rulesets if it's useful to do so.

Any comments?
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Akira TAGOH