Add NL.FR-NL-1.01 testcase

[aaroncameron-wk]

Reason for change

FR-NL-1.01: A BOM character MUST NOT be used
A BOM (Byte Order Mark) is a unicode character that represents the byte order in a file:
16 or 32 bits. Within the UTF-8 standard, this is an optional, but unnecessary, character (because the 8
stands for 8 bits).
This rule cannot be implemented using XBRL Formula since the BOM
character is a physical document attribute that is not available in the logical document model
used by XPath.

Description of change

Like the validation checking for a CDATA end sequence, we shouldn't rely on a parsed XML model to find this character, as there's no guarantee that XML parsing won't trim/ignore it wherever it may be included in a document. This PR makes a reusable findDisallowedPatterns function (with a cached result so the instance documents don't need to be loaded multiple times) to check for the CDATA sequence, a BOM character, or any other pattern that makes sense to be checked for this way.

Steps to Test

CI

review:
@Arelle/arelle

[allenbross-wf]

QA +10 CI Passed successfully