wide strings match only UTF16-LE

Describe the bug The example string "Borland" from https://yara.readthedocs.io/en/v4.2.3/writingrules.html#wide-character-strings is there encoded as B\x00o\x00r\x00l\x00a\x00n\x00d\x00 but that's just the LE version of UTF16 with BE being\x00B\x00o\x00r\x00l\x00a\x00n\x00d (\x00 in front). So the example rule from the docs doesn't match UTF16-BE:

rule WideCharTextExample1
{
    strings:
        $wide_string = "Borland" wide

    condition:
        $wide_string
}

UTF16-LE is by far the most common case but I stumbled upon the string Qi Lijun in UTF16-BE in 2fb7a38e69a88e3da8fece4c6a1a81842c1be6ae9d6ac299afa4aef4eb55fd4b (however that happened ...)

(Actually this is more unexpected behavior than a bug but that fits better than a feature request.)

To Reproduce

rule WideCharTextExample1
{
    strings:
        $wide_string = "Qi Lijun" wide

    condition:
        $wide_string
}

Doesn't match:

$ yara test.yar 2fb7a38e69a88e3da8fece4c6a1a81842c1be6ae9d6ac299afa4aef4eb55fd4b

Expected behavior There would be several options to handle the problem:

1. Back to the Borland example, the perfect solution would be to search for both UTF16-LE and UTF16-BE. UTF16-LE: B\x00o\x00r\x00l\x00a\x00n\x00d\x00 UTF16-BE: \x00B\x00o\x00r\x00l\x00a\x00n\x00d

2. The faster and memory saving would be to strip the \x00 in the end of the existing implementation and search for: B\x00o\x00r\x00l\x00a\x00n\x00d

That might hit wrong on very short strings (which shouldn't happen that often because of the performance and false positive problems).

1. Introduce e.g. widebe as a new string modifier, similar to uint16be.

2. Explain the issue in the docs and recommend to use hex for UTF16-BE.

Please complete the following information:

• OS: Linux
• YARA version: 4.3.0

Additional context This also affects string search on VT. This search doesn't show any results: content:"Qi Lijun" tag:peexe This shows 10 hits: content:{00 51 00 69 00 20 00 4c 00 69 00 6a 00 75 00 6e} (same string in hex(UTF16-BE) )