Lua Branch Testing

[junoocha]

PR to test the workout regarding String operations. Will be closed after testing.

[enki-hq]

Insight previews:

• [ ] enkidevs/curriculum/lua/lua-core/operators-in-lua-iv/concatenation-operator-in-lua.md
• [ ] enkidevs/curriculum/lua/lua-core/operators-in-lua-iv/length-operators-in-lua-i.md
• [ ] enkidevs/curriculum/lua/lua-core/operators-in-lua-iv/operator-precedence-in-lua-i.md
• [ ] enkidevs/curriculum/lua/lua-core/operators-in-lua-iv/operator-precedence-in-lua-ii.md