Release v0.5.4

What's Changed

• docs: custom data docs by @Brazol in #758
• chore(llc): regular push notifications handling by @Brazol in #762
• fix(llc): fixed foreground service being recreated when declining the call by @Brazol in #764
• chore(dogfooding): enhanced dogfooding readme by @Brazol in #765
• chore: remove the deprecated flutter_background package by @Brazol in #763
• chore: dependencies update by @Brazol in #755
• Release v0.5.4 by @Brazol in #766

Full Changelog: v0.5.3...v0.5.4