should ignore BOM in .gitignore

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Reproduction steps

1. Try this with an existing repo. Put a BOM at the header of a .gitignore file, and a directory to ignore such as .vs/ on the same (top, first) line of the .gitignore file.
2. confirm command-line native git still ignores the .vs directory.
3. Write a quick program that uses libgit2sharp to look at the above repo and get the status.
4. Get the status and note the status is marked dirty, and the .vs dir is listed as untracked, not ignored.

Expected behavior

The status reported by libgit2sharp should report status is clean. It should ignore the .vs dir.

Actual behavior

The .vs dir is listed as untracked, not ignored.

The status is dirty.

Version of LibGit2Sharp (release number or SHA1)

0.26.2

Operating system(s) tested; .NET runtime tested

Windows 10

Tái hiện báo cáo với LibGit2Sharp 0.26.2 trên Windows 10 bằng cách sử dụng một .gitignore có dòng đầu tiên bắt đầu bằng BOM và nêu tên .vs. So sánh trạng thái của nó với Git gốc. Hoàn tất khi LibGit2Sharp báo cáo trạng thái sạch và đánh dấu .vs là bị bỏ qua thay vì chưa được theo dõi.