Update Zawgyi locale to Qaag

CLDR is proposing the script code Qaag to use for Zawgyi text:

> Qaag is a special script code for identifying the non-standard use of Myanmar characters for display with the Zawgyi font. The purpose of the code is to enable migration to standard, interoperable use of Unicode by providing an identifier for Zawgyi for tagging text, applications, input methods, font tables, transformations, and other mechanisms used for migration.

corpuscrawler should be updated to use the new script code instead of the `-u-s0-zawgyi` workaround. Myanmar Tools will need to also be updated to consume the new script code.