Check for UTF-8 Byte Order Mark Preamble at the start of stream.

[AristurtleDev]

Description

As shown in #1073, it's possible for a scenario to occur where someone edits a Bitmap Font (BMFont) file using a third party library that then saves it back with the UTF-8 Byte Order Mark (BOM) preamble. When this happens, the signature check of the file fails causing an exception to to be thrown.

To resolve this, a check for the preamble is made, and if found, skips it.

Related Issues/Tickets

• Closes MonoGame.Extended won't load XML format .fnt files if they begin with the byte order mark #1073

Changes Made

• Added unit test to ensure BOM check is performed.
• Checks for UTF-8 Byte Order Mark (BOM) Preamble at the start of stream when reading a BMFont file.

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