[gatsby-remark-embed-snippet]: lack of snippet options

[edukisto]

Description

This is a feature request.

gatsby-remark-embed-snippet does not allow to use any of gatsby-remark-prismjs snippet options, such as numberLines, outputLines, promptHost, promptUser, and a nameless option for highlighting lines.

Steps to reproduce

See a reproduction.

1. Create a source file:

   echo "echo 'obase=18; 4 * 5' | bc | sed 's/[ 0]//g'
   12
   echo 'obase=21; 4 * 6' | bc | sed 's/[ 0]//g'
   13
   echo 'I shall never get to twenty at that rate!'" > example.sh

2. Use gatsby-remark-embed-snippet to embed the content of the source file in a Markdown file:

   `embed:example.sh`

3. Run gatsby develop.

   

4. Add options for gatsby-remark-prismjs:

   `embed:example.sh{5}{numberLines: true}{outputLines: 2,4}{promptHost: wonderland}{promptUser: alice}`

   However, the original syntax is error-prone. It's better to use a single JSON5 object instead: embed:example.sh{highlightRange: 5, numberLines: true, outputLines: "2,4", promptHost: "wonderland", promptUser: "alice"}. The highlightRange option is a replacement for the nameless option for highlighting lines.

5. Gatsby throws an exception.

Expected result

I would like to have the same output as if I wrote the following:

```shell{5}{numberLines: true}{outputLines: 2,4}{promptHost: wonderland}{promptUser: alice}
echo 'obase=18; 4 * 5' | bc | sed 's/[ 0]//g'
12
echo 'obase=21; 4 * 6' | bc | sed 's/[ 0]//g'
13
echo 'I shall never get to twenty at that rate!'
```

This works great with gatsby-remark-prismjs.

Actual result

Error: Invalid snippet options specified: {5}{numberLines: true}{outputLines: 2,4}{promptHost: wonderland}{promptUser: alice}

Environment

  System:
    OS: Linux 5.4 Ubuntu 20.04.1 LTS (Focal Fossa)
    CPU: ...
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Node: 15.5.0 - ~/.nvm/versions/node/v15.5.0/bin/node
    npm: 7.3.0 - ~/.nvm/versions/node/v15.5.0/bin/npm
  ...
  npmGlobalPackages:
    gatsby-cli: 2.16.2