Force LF style line endings in all text files

[mtreinish]

Summary

As a repository we need to have consistent line endings so that we can resolve diffs sanely. Right now we haven't had an opinion on this. But some CRLF line endings caused major merge conflicts on #13278 and was preventing unraveling an otherwise simple merge conflict resolution. This commit sets a global default to use LF line endings for all text files to prevent such issues in the future.

Details and comments

The two release note files were normalized by git after adding the .gitattributes file.

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 13568284676

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.003%) to 87.863%

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Files with Coverage Reduction	New Missed Lines	%
crates/accelerate/src/unitary_synthesis.rs	1	94.39%
crates/qasm2/src/lex.rs	3	91.98%

Totals
Change from base Build 13553732677:	0.003%
Covered Lines:	77534
Relevant Lines:	88244

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💛 - Coveralls

[1ucian0]

Somehow, it breaks the visual testing?

[jakelishman]

The LaTeX and text-drawer tests use the same filecmp.cmp function as the image tests, which ofc opens the files in binary read mode, so does no line conversions. On Windows, we're writing out the files with \r\n line endings from Python space, but the references always have \n. We can either modify the .gitattributes so that test/python/visualization/references/*.{txt,tex} retains platform-native linefeeds (it's like eol=native or something), or modify the test function to pass a binary=False/binary=True flag.