Add rspec file for smallest integer
user
```ruby
require_relative "my_solution"

describe 'smallest_integer' do
  it "returns nil when the array is empty ([])" do
    expect(smallest_integer([])).to be_nil
  end

  it "returns 0 when that is the only element in the array" do
    expect(smallest_integer([0])).to eq 0
  end

  it "returns -10 when that is the only element in the array" do
    expect(smallest_integer([-10])).to eq -10
  end

  it "returns -10 for [-10, 0, 10]" do
    expect(smallest_integer([-10, 0, 10])).to eq -10
  end

  it "returns 1 for [1, 2, 3]" do
    expect(smallest_integer([1, 2, 3])).to eq 1
  end

  it "returns -30 for [-10, -20, -30]" do
    expect(smallest_integer([-10, -20, -30])).to eq -30
  end

  it "returns the smallest positive integer regardless of ordering" do
    array = (1..100).to_a.shuffle

    expect(smallest_integer(array)).to eq 1
  end

  it "returns the smallest negative integer regardless of ordering" do
    array = (-100..-10).to_a.shuffle

    expect(smallest_integer(array)).to eq -100
  end
end```
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