a11y: Expose GTK_ACCESSIBLE_RELATION_DETAILS to at-spi2
This particular relation was not exposed to at-spi2. Exposing it required adding a missing at-spi2 relation variant, but it was introduced in at-spi2-core 2.26, so that's likely safe as well.
This particular relation was not exposed to at-spi2. Exposing it required adding a missing at-spi2 relation variant, but it was introduced in at-spi2-core 2.26, so that's likely safe as well.