CustomString Starts with and Ends with

[bi3mer]

Add these string extension methods and include a link to https://docs.unity3d.com/Manual/BestPracticeUnderstandingPerformanceInUnity5.html in each function comments to explain why it is added.

Please update the bracketing style of this

public static bool CustomEndsWith(string a, string b) {
    int ap = a.Length - 1;
    int bp = b.Length - 1;

    while (ap >= 0 && bp >= 0 && a [ap] == b [bp]) {
        --ap;
        --bp;
    }
    return (bp < 0 && a.Length >= b.Length) || (ap < 0 && b.Length >= a.Length);
}

public static bool CustomStartsWith(string a, string b) {
    int aLen = a.Length;
    int bLen = b.Length;
    int ap = 0; int bp = 0;

    while (ap < aLen && bp < bLen && a [ap] == b [bp]) {
        ++ap;
        ++bp;
    }

    return (bp == bLen && aLen >= bLen) || (ap == aLen && bLen >= aLen);
}