doc,punycode: use code markup/markdown in headers

Backport-PR-URL: #31108
PR-URL: #31086
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc/api/punycode.md

@@ -37,7 +37,7 @@ The `punycode` module is a third-party dependency used by Node.js and
 made available to developers as a convenience. Fixes or other modifications to
 the module must be directed to the [Punycode.js][] project.
 
-## punycode.decode(string)
+## `punycode.decode(string)`
 <!-- YAML
 added: v0.5.1
 -->
@@ -52,7 +52,7 @@ punycode.decode('maana-pta'); // 'mañana'
 punycode.decode('--dqo34k'); // '☃-⌘'
 ```
 
-## punycode.encode(string)
+## `punycode.encode(string)`
 <!-- YAML
 added: v0.5.1
 -->
@@ -67,7 +67,7 @@ punycode.encode('mañana'); // 'maana-pta'
 punycode.encode('☃-⌘'); // '--dqo34k'
 ```
 
-## punycode.toASCII(domain)
+## `punycode.toASCII(domain)`
 <!-- YAML
 added: v0.6.1
 -->
@@ -86,7 +86,7 @@ punycode.toASCII('☃-⌘.com');   // 'xn----dqo34k.com'
 punycode.toASCII('example.com'); // 'example.com'
 ```
 
-## punycode.toUnicode(domain)
+## `punycode.toUnicode(domain)`
 <!-- YAML
 added: v0.6.1
 -->
@@ -104,12 +104,12 @@ punycode.toUnicode('xn----dqo34k.com');  // '☃-⌘.com'
 punycode.toUnicode('example.com');       // 'example.com'
 ```
 
-## punycode.ucs2
+## `punycode.ucs2`
 <!-- YAML
 added: v0.7.0
 -->
 
-### punycode.ucs2.decode(string)
+### `punycode.ucs2.decode(string)`
 <!-- YAML
 added: v0.7.0
 -->
@@ -125,7 +125,7 @@ punycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]
 punycode.ucs2.decode('\uD834\uDF06'); // [0x1D306]
 ```
 
-### punycode.ucs2.encode(codePoints)
+### `punycode.ucs2.encode(codePoints)`
 <!-- YAML
 added: v0.7.0
 -->
@@ -140,7 +140,7 @@ punycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'
 punycode.ucs2.encode([0x1D306]); // '\uD834\uDF06'
 ```
 
-## punycode.version
+## `punycode.version`
 <!-- YAML
 added: v0.6.1
 -->