Add ShopSync support (#26) ...

* feat: add shopSync options to config.example.lua

* docs: document shopSync settings

* feat: get as much of the shopsync support done as possible before I go to work

* fix: typos, version.txt finding & gps

* feat: broadcast products in ShopSync message

* chore: revert repo owner in installer.lua

* chore: remove unneccesary .gitignore entry I made

* fix: missing comma in config

* style: extract ctx.config.shopSync to it's own variable, remove rendundant parenthesis

* refactor: create utils.isNullish helper, improve how GPS location is stored & move enabled check to init.lua

* fix: my stupidity

* fix: backwards compatibility with older configs

* fix: shopsync no longer initially reports 0 stock

* fix: wait for chests to be refreshed instead of doing it ourselves