chore(deps): bump proc-macro2 from 1.0.80 to 1.0.81 (#30)

Bumps [proc-macro2](https://github.com/dtolnay/proc-macro2) from 1.0.80
to 1.0.81.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/dtolnay/proc-macro2/releases">proc-macro2's
releases</a>.</em></p>
<blockquote>
<h2>1.0.81</h2>
<ul>
<li>Documentation improvements</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/fd2c998967a65d3378f06f2480abd4d34f4697ab"><code>fd2c998</code></a>
Release 1.0.81</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/f965e17679d18e0049406913588458b12fbad871"><code>f965e17</code></a>
Merge pull request <a
href="https://redirect.github.com/dtolnay/proc-macro2/issues/453">#453</a>
from dtolnay/delimiternone</li>
<li><a
href="https://github.com/dtolnay/proc-macro2/commit/69fd060280b3ddd5c3678ebdd9eb4446619cc86f"><code>69fd060</code></a>
Sync documentation of Delimiter::None</li>
<li>See full diff in <a
href="https://github.com/dtolnay/proc-macro2/compare/1.0.80...1.0.81">compare
view</a></li>
</ul>
</details>
<br />


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</details>

Cargo.toml

@@ -18,7 +18,7 @@ keywords = ["enum", "string", "derive", "macro"]
 proc-macro = true
 
 [dependencies]
-proc-macro2 = "1.0.80"
+proc-macro2 = "1.0.81"
 quote = "1.0.36"
 syn = "2.0.59"