ICU4X 0.3.0

ICU4X 0.3.0 contains major improvements to the data pipeline, as well as bug fixes and feature work.

• Static data provider without filesystem dependency (#78)
• Infrastructure around zero-copy deserialization, including ZeroVec and Yoke (#652, #667)
• Most ICU4X components support no_std (#812)
• Hour cycle preferences are used by DateTimeFormat (#671)
• Skeleton matching supports additional field widths (#584)
• Add canonicalize method to LocaleCanonicalizer (#747)
• Added range iterator on UnicodeSet (#836)
• Add PluralRules::categories() function (#789)
• Consolidated data generation tool into new binary icu4x-datagen