Parse files with byte-order-mark

[am11]

When parsing a JSON file with BOM such as:

https://github.com/dotnet/toolset/blob/40cc5860e2ef311b9aca733b1d2eccaa681bd422/TestAssets/InstallationScriptTests/InstallationScriptTests.json

JSON.sh gives the following error:

EXPECTED EOF GOT {

Current workaround is to strip these characters using tool like awk: awk 'NR==1{sub(/^\xef\xbb\xbf/,"")}1' "$json_file" | sh JSON.sh | .....

It would be nice if parser skip these BOM characters and start parsing after the offset. It will save consumers from stripping these characters.