Support float16 ndarray data type

[eslavich]

Add support for reading ndarray with float16 data type.

Closes #18

[github-actions]

Overall Project	61.75% -0.5%	🍏
Files changed	87.95%	🍏

Module	Coverage
asdf-core	61.89% -0.51%	🍏

Files

Module	File	Coverage
asdf-core	DataTypes.java	99.18%	🍏
	Float16Utils.java	98.9% -1.1%	🍏
	NdArrayHandler_1_x.java	74.85%	🍏
	FloatNdArrayImpl.java	53.08% -18.46%	🍏
	InlineBlockV1_0_0.java	46.61%	🍏
	DoubleNdArrayImpl.java	46.55%	🍏
	BigDecimalNdArrayImpl.java	9.09% -8.46%	❌

[github-actions]

Overall Project	61.75% -0.5%	🍏
Files changed	87.95%	🍏

Module	Coverage
asdf-core	61.89% -0.51%	🍏

Files

Module	File	Coverage
asdf-core	DataTypes.java	99.18%	🍏
	Float16Utils.java	98.9% -1.1%	🍏
	NdArrayHandler_1_x.java	74.85%	🍏
	FloatNdArrayImpl.java	53.08% -18.46%	🍏
	InlineBlockV1_0_0.java	46.61%	🍏
	DoubleNdArrayImpl.java	46.55%	🍏
	BigDecimalNdArrayImpl.java	9.09% -8.46%	❌