[DOCS] Add more example .dmai programs (fizzbuzz, fibonacci, गणित, यादृच्छिक)

[alphacrack]

examples/ has 5 programs (hello, person, calculator, shopping_list, error). More small, idiomatic examples make the language easier to learn — and every example is automatically smoke-tested by CI (tests/test_smoke.py runs each one), so an example PR is a real, verified contribution.

Wanted (one PR each is fine):

• fizzbuzz / number games (great once elif [BUG] No elif mapping — नहि त यदि transpiles to invalid else if #25 lands)
• Fibonacci or factorial (recursion with कार्य)
• Using the गणित (math) module — sqrt, pi
• Using यादृच्छिक (random) — dice roll
• String building / greeting program

Rules: must run under the sandbox (whitelisted modules only, no open), keep it under ~30 lines. error.dmai is the only intentionally-broken example — keep new ones working.

Good first issue — no Python internals needed, just working Maithili code. Maithili speakers especially welcome: idiomatic naming makes these teaching material.