Allow analysis of inline styles specificity

[bartveneman]

projectwallace.com/analyze-css is capable of scraping inline styles, which means we're not limited to a 3-number specificity tuple ([0,0,0]). We could allow a specific selector name that would be recognised as an inline style, setting the specificity to [1,0,0,0]. This could or maybe should be a configurable option., so other tools could set their own selector preference.