Quote is required even if it begins with backquote.

[k1LoW]

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Hi @goccy!

I noticed when using a mix of goccy/go-yaml and go-yaml/yaml that backquotes also cannot be used at the beginning of a token.

https://go.dev/play/p/ysabzaYClh3

I also got an error at https://www.yamllint.com/.

According to https://yaml.org/spec/1.2.2/ backquote (`) is reserved.

The “@” (x40, at) and “`” (x60, grave accent) are reserved for future use.

Thank you.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #440 +/- ## ======================================= Coverage 76.02% 76.02% ======================================= Files 13 13 Lines 4692 4692 ======================================= Hits 3567 3567 Misses 866 866 Partials 259 259 ```