CamelCase method incorrectly handles PascalCase and camelCase

[JuicyLung91]

Describe the bug
The CamelCase method in the package is currently not handling PascalCase and camelCase strings correctly. Specifically, the method converts both lower case of the input when the input is written in PascalCase or CamelCase.

To Reproduce

• Use the CamelCase method with the input TestEntity.
• Use the CamelCase method with the input testEntity.
• Observe that both inputs are converted to testentity.

Expected behavior
TestEntity should be converted to testEntity.
testEntity should remain testEntity.

Additional context
you can run this test

func TestCamelCaseHelper(t *testing.T) {
	tests := []struct {
		input    string
		expected string
	} {
		{"test", "test"},
		{"test entity", "testEntity"},
		{"test-entity", "testEntity"},
		{"test-entity_test", "testEntityTest"},
		{"test_entity", "testEntity"},
		{"TestEntity", "testEntity"},
		{"testEntity", "testEntity"},
		{"test_entity_definition", "testEntityDefinition"},
	}

	for _, test := range tests {
		actual := stringy.New(test.input).CamelCase().Get()
		if actual != test.expected {
			t.Errorf("Expected %s, got %s, input: %s", test.expected, actual, test.input)
		}
	}
}