[css-fonts] Cross-link to CSS Text order of operations

[fantasai]

https://lists.w3.org/Archives/Public/www-style/2015Feb/0328.html

Done for CSS Writing Modes already in 78a99ed

[svgeesus]

Rather than the Introduction, which solely deals with fonts, it looks like the section 6.1. Glyph selection and positioning, which also deals with text layout, would be the best place to insert this reference.

Here is my suggested text (to be appended to the first paragraph of that section:

The point at which font selection and positioning happens in the overall order of text processing operations (such as text transformation, text orientation and text alignment) is described in [[css-text-3#order]]