Support <code> tags and blocks

[jfhr]

• deltaToHtml: convert { insert: "foo", attributes: { code: true } } objects to <code>foo</code>
• htmlToDelta: convert <code>foo</code> to { insert: "foo", attributes: { code: true } }
• deltaToHtml: convert { insert: "foo" }, { insert: "\n", attributes: { "code-block": true, /*...*/ } } to <pre><code>foo</code></pre>
• htmlToDelta: convert <pre><code>foo</code></pre> to { insert: "foo" }, { insert: "\n", attributes: { "code-block": true, /*...*/ } }
• deltaToNpf: convert { insert: "foo", attributes: { code: true } } to colored text
• deltaToNpf: convert { insert: "\n", attributes: { "code-block": true, /*...*/ } } to chat text subtype

[jfhr]

Looks like npf has a chat text subtype, which is displayed in monospace font. That might be the best choice for code. See https://www.tumblr.com/docs/npf#:~:text=official%20Tumblr%20clients%20display%20this%20with%20a%20monospace%20font

[jfhr]

unfortunately the npf subtype chat is only for whole blocks and doesn't work inline. Might just use a red color for code instead ?

[jfhr]

Added requirement for code blocks. Code blocks will be converted to npf chat text subtype, inline code to red colored text

[jfhr]

Looks like the conditional access operator foo?.bar doesn't work in node 12. should have known