… apply it properly

Since bazelbuild#161 removed HTML escaping for defaults and function docstrings,
we should do the same for attribute and param docs in table cells.

The only limitations Markdown places on table cells are:
* no pipe characters (they must be escaped with a backslash)
* no newlines (they must be transformed into <br> or an HTML entity)

The latter restriction makes it impossible to have a fenced code block
inside a table cell.

Therefore:
* we do not escape HTML or Markdown markup outside a fenced code block
* we keep existing logic for escaping newlines outside a fenced code
  block
* we fix fence detection (e.g. allowing more than 3 fence characters to
  support embedded code blocks in code blocks, allowing tildes as fence
  characters, properly handling language names, etc.);
* in code block content, we escape HTML, and we escape newlines as HTML
  entities (since <br> does not work in a <pre><code> block) - finally
  fixing code block newlines in table cells.

This is a followup to bazelbuild#161.

… apply it properly

Since bazelbuild#161 removed HTML escaping for defaults and function docstrings,
we should do the same for attribute and param docs in table cells.

The only limitations Markdown places on table cells are:
* no pipe characters (they must be escaped with a backslash)
* no newlines (they must be transformed into <br> or an HTML entity)

The latter restriction makes it impossible to have a fenced code block
inside a table cell.

Therefore:
* we do not escape HTML or Markdown markup outside a fenced code block
* we keep existing logic for escaping newlines outside a fenced code
  block
* we fix fence detection (e.g. allowing more than 3 fence characters to
  support embedded code blocks in code blocks, allowing tildes as fence
  characters, properly handling language names, etc.);
* in code block content, we escape HTML, and we escape newlines as HTML
  entities (since <br> does not work in a <pre><code> block) - finally
  fixing code block newlines in table cells.

This is a followup to bazelbuild#161.

… apply it properly (#167)

In Markdown table cells, apply HTML escaping only to code blocks, and apply it properly

Since #161 removed HTML escaping for defaults and function docstrings, we should do the same for attribute and param docs in table cells.

The only limitations Markdown places on table cells are:
* no pipe characters (they must be escaped with a backslash)
* no newlines (they must be transformed into `<br>` or an HTML entity)

The latter restriction makes it impossible to have a fenced code block inside a table cell.

Therefore:
* we do not escape HTML or Markdown markup outside a fenced code block
* we keep existing logic for escaping newlines outside a fenced code block
* we fix fence detection (e.g. allowing more than 3 fence characters to support embedded code blocks in code blocks, allowing tildes as fence characters, properly handling language names, etc.);
* in code block content, we escape HTML, and we escape newlines as HTML entities (since `<br>` does not work in a `<pre><code>` block) - finally fixing code block newlines in table cells.
    
This is a followup to #161.

Partially addresses #118