feat: syntax highlighting

[Jay-Karia]

Adds syntax highlighting to converted command.
Returns an html string.

API

highlight(command, theme)

param: command : string
param: theme : "light" | "dark" with default "light"

Usage

highlight("npm run dev", "dark")

Returns

 <pre class="shiki github-dark" style="background-color:#24292e;color:#e1e4e8" tabindex="0"><code><span class="line"><span style="color:#B392F0">npm</span><span style="color:#9ECBFF"> run</span><span style="color:#9ECBFF"> dev</span></span></code></pre>

Closes #49

[nebrelbug]

Looks good! I think it might be better as a separate function though.

[Jay-Karia]

@nebrelbug and what about #53 ?

[Jay-Karia]

Async / Await does not seem to work in rollup

It returns a Promise first then the html string, even after using await

[Jay-Karia]

Problems in testing using jest.
It has some problem related to the import statement for shiki

[nebrelbug]

As I'm thinking about this, I don't know if this functionality belongs in npm-to-yarn. If a user wants to display the command in a codeblock, they can add syntax highlighting with shiki themselves pretty easily.

[Jay-Karia]

It would be an add on for the library.
Can improve the asthetics of the output.

If we discontinue this, what about #60

[nebrelbug]

I think it might be nice as a separate package to integrate.

The rest of #60 looks good to me though.