Insert space around the multiplication operator

[yukukotani]

Fixes #576

Inserts space around the multiplication operator, but not for spread operator.

Current

// No error
fun main() {
    test(*array)
    test(1, *array, 2)
    test(1*value)
    test.run { 1*value }
}

Patched

fun main() {
    test(*array)
    test(1, *array, 2)
    // Missing spacing around "*"
    test(1*value)
    // Missing spacing around "*"
    test.run { 1*value }
}

// Formatted result
fun main() {
    test(*array)
    test(1, *array, 2)
    test(1 * value)
    test.run { 1 * value }
}

[Tapchicoma]

Thank you for your contribution 👍