docs: fix incorrect union type explanation- Corrected A | B explanati…

[Aditya-myst]

Description

Fixes incorrect explanation of TypeScript union types in the documentation.

The Issue

The documentation incorrectly stated that A | B means "A or B or both at once".
This is incorrect - union types represent exactly one type or the other, not both simultaneously.

Changes Made

• Corrected the explanation to clarify that A | B means "either A or B"
• Added clarification about intersection types A & B for "both at once" scenario
• Added note about property access requiring type guards
• Updated docs/basic/troubleshooting/types.md (README.md will auto-generate from this)

Example

type Foo = { a: number } | { b: string }
const invalid: Foo = { a: 1, b: 'two' } // ❌ Error - not assignable  
const valid: Foo = { a: 1 }             // ✅ Correct

[filiptammergard]

Thanks!