Handle echo option to fix #309

[denius]

Without tests, I don't know how to do them.

[denius]

In a bit more detail:
the qmd document is converted to the following ipynb

---
engine: julia
---

```{julia}
#| echo: false
using PythonCall
```

```{python}
print("option `echo:`")
```

```{python}
#| echo: false
print("option `echo: false`")
```

```{python}
#| echo: true
print("option `echo: true`")
```

```{python}
#| echo: fenced
print("option `echo: fenced`")
```

{
    "metadata": {
        "kernelspec": {
            "display_name": "Julia 1.11.5",
            "language": "julia",
            "name": "julia-1.11.5"
        },
        "kernel_info": {
            "name": "julia"
        },
        "language_info": {
            "name": "julia",
            "version": "1.11.5",
            "codemirror_mode": "julia"
        }
    },
    "nbformat": 4,
    "nbformat_minor": 5,
    "cells": [
        {
            "id": "1",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
                "---\n",
                "engine: julia\n",
                "---"
            ]
        },
        {
            "id": "2",
            "cell_type": "code",
            "metadata": {
            },
            "source": [
                "#| echo: false\n",
                "using PythonCall"
            ],
            "outputs": [
            ],
            "execution_count": 1
        },
        {
            "id": "3",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
            ]
        },
        {
            "id": "4_code_prefix",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
                "```python\n",
                "print(\"option `echo:`\")\n",
                "```"
            ]
        },
        {
            "id": "4",
            "cell_type": "code",
            "metadata": {
            },
            "source": [
                "#| echo: false\n",
                "print(\"option `echo:`\")"
            ],
            "outputs": [
                {
                    "output_type": "stream",
                    "name": "stdout",
                    "text": "option `echo:`\n"
                }
            ],
            "execution_count": 1
        },
        {
            "id": "5",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
            ]
        },
        {
            "id": "6_code_prefix",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
            ]
        },
        {
            "id": "6",
            "cell_type": "code",
            "metadata": {
            },
            "source": [
                "#| echo: false\n",
                "print(\"option `echo: false`\")"
            ],
            "outputs": [
                {
                    "output_type": "stream",
                    "name": "stdout",
                    "text": "option `echo: false`\n"
                }
            ],
            "execution_count": 1
        },
        {
            "id": "7",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
            ]
        },
        {
            "id": "8_code_prefix",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
                "```python\n",
                "print(\"option `echo: true`\")\n",
                "```"
            ]
        },
        {
            "id": "8",
            "cell_type": "code",
            "metadata": {
            },
            "source": [
                "#| echo: false\n",
                "print(\"option `echo: true`\")"
            ],
            "outputs": [
                {
                    "output_type": "stream",
                    "name": "stdout",
                    "text": "option `echo: true`\n"
                }
            ],
            "execution_count": 1
        },
        {
            "id": "9",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
            ]
        },
        {
            "id": "10_code_prefix",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
                "```{{python}}\n",
                "print(\"option `echo: fenced`\")\n",
                "```"
            ]
        },
        {
            "id": "10",
            "cell_type": "code",
            "metadata": {
            },
            "source": [
                "#| echo: false\n",
                "print(\"option `echo: fenced`\")"
            ],
            "outputs": [
                {
                    "output_type": "stream",
                    "name": "stdout",
                    "text": "option `echo: fenced`\n"
                }
            ],
            "execution_count": 1
        },
        {
            "id": "11",
            "cell_type": "markdown",
            "metadata": {
            },
            "source": [
            ]
        }
    ]
}

[MichaelHatherly]

Thanks @denius, when I get some available time I will take a look and the implementation and review.

[codecov]

Codecov Report

Attention: Patch coverage is 61.53846% with 10 lines in your changes missing coverage. Please review.

Project coverage is 79.17%. Comparing base (5b96923) to head (5bd9a30).

Files with missing lines	Patch %	Lines
src/server.jl	61.53%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #311      +/-   ##
==========================================
- Coverage   79.40%   79.17%   -0.24%     
==========================================
  Files          39       39              
  Lines        2064     2089      +25     
==========================================
+ Hits         1639     1654      +15     
- Misses        425      435      +10     

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