feat: add instructions on how to include canbench in Github CI

[ielashi]

We also use those same instructions to include the examples in our own CI.

[github-actions]

canbench 🏋 (dir: examples/btreemap_vs_hashmap)

No significant performance changes detected ✅

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Benchmark: insert_users
  total:
    instructions: 2.56 B (no change)
    heap_delta: 871 pages (no change)
    stable_memory_delta: 0 pages (no change)

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Benchmark: remove_users
  total:
    instructions: 2.06 B (no change)
    heap_delta: 0 pages (no change)
    stable_memory_delta: 0 pages (no change)

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Benchmark: pre_upgrade_bench
  total:
    instructions: 717.11 M (no change)
    heap_delta: 519 pages (no change)
    stable_memory_delta: 184 pages (no change)

  serialize_state (profiling):
    instructions: 717.10 M (no change)
    heap_delta: 519 pages (no change)
    stable_memory_delta: 0 pages (no change)

  writing_to_stable_memory (profiling):
    instructions: 502 (no change)
    heap_delta: 0 pages (no change)
    stable_memory_delta: 184 pages (no change)

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[github-actions]

canbench 🏋 (dir: examples/fibonacci)

No significant performance changes detected ✅

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Benchmark: fibonacci_20
  total:
    instructions: 2301 (no change)
    heap_delta: 0 pages (no change)
    stable_memory_delta: 0 pages (no change)

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Benchmark: fibonacci_45
  total:
    instructions: 3088 (no change)
    heap_delta: 0 pages (no change)
    stable_memory_delta: 0 pages (no change)

---------------------------------------------------