`switch_to_uppercase`

Changes all selected letters to uppercase.

--- Examples ---

┌──────────────────────────────────┐     ┌──────────────────────────────────┐
│ This (wOrD] should be uppercase. │ --> │ This (WORD] should be uppercase. │
└──────────────────────────────────┘     └──────────────────────────────────┘