findBestAppIcon should choose the last among equally suitable icons, not the first

[cairomassimo]

Per https://w3c.github.io/manifest/#icons-member:

If there are multiple equally appropriate images in icons, a user agent MUST use the last one declared in order at the time that the user agent collected the list of icons.

PWABuilder should mimic user agents and follow this rule, but does not.

See:

PWABuilder/apps/pwabuilder/src/script/utils/icons.ts

Line 35 in 373a64c

const exactMatch = iconInfos.find(i => i.isExactMatch(purpose, desiredWidth, desiredHeight, mimeType));

[cairomassimo]

Thank you! <3