Allow bare CR newlines

[hukkin]

Preparation for an upcoming TOML version that allows bare CR newlines (see toml-lang/toml#837 (comment))

[codecov-commenter]

Codecov Report

Merging #10 (eaee2c8) into master (889a15d) will not change coverage.
The diff coverage is 100.00%.

❗ Current head eaee2c8 differs from pull request most recent head 359cfe6. Consider uploading reports for the commit 359cfe6 to get more accurate results

@@            Coverage Diff            @@
##            master       #10   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          118        92   -26     
  Branches        34        26    -8     
=========================================
- Hits           118        92   -26     

Impacted Files	Coverage Δ
tomli_w/_writer.py	100.00% <100.00%> (ø)

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