[tools] Doc tool does not escape union types in markdown table

[zflat]

Bug Report

I have a schema that uses the union to specify the type of an attribute and when I run the doc tool, the markdown output contains a pipe which results in an extra column in the table and the type following the pipe in the wrong column in the table.

1. Minimal reproduce step (Required)

1. Create a new module test

   kcl mod init test && cd test
   

2. Create a schema file with the contents:

   schema x:
       a: int | str  # attribute a could be a int or string
   

3. Run the doc tool

2. What did you expect to see? (Required)

I expected to see the int | str as the type column in the markdown table.

Acceptable output would have the pipe escaped:

Here is the relevant output:

| name | type | description | default value |
| --- | --- | --- | --- |
|**a** `required`|int \| str|||

3. What did you see instead (Required)

Instead, I see the str in the wrong column in the markdown table because the table has too many pipes. The pipe character should be escaped.

Here is the relevant output markdown:

| name | type | description | default value |
| --- | --- | --- | --- |
|**a** `required`|int | str|||

This is what the table looks like:

name	type	description	default value
a required	int	str

4. What is your KCL components version? (Required)

$ kcl --version
kcl version 0.11.0-alpha.1

[Peefy]

You can use the --escape-html flag to prevent this issue.

Perhaps we can set this flag to default to true in the KCL CLI. cc @zong-zhe @He1pa