Changes:
- Removed action bar message "transferring container...".
- Now, all plugin-produced action-bar messages (right now it is only extra-weight-damage message) can be enabled/disabled. Once they disabled, they will be redirected to player chat-messages.
- Fixed player armor swap glitch with backpack.
- Now, backpack visualization will be force-removed if player's backpack just disappeared somehow.
- Fixed container inventory weight calculations.
- Now, you can set weight-speed penalty.
- Added more properties to plugin's config.

Possible future improvements:
- I've tried to make my plugin depend on kotlin-stdlib plugin ( https://www.spigotmc.org/resources/kotlin-stdlib.80808/) to reduce my plugin file size. However, its current version 1.9.10 is not compatible with my used kotlin-stdlib version, which is 1.9.21. Once their plugin will be updated and compatible with my plugin, I will make an update for my plugin with reduced file size (excluded Kotlin dependencies).
- Feature: container's health points - containers will get their own health points, explosions will "damage" containers by reducing their health points; thus, if the health points reach zero, they will break and their contents will be dropped.