Perfect whitespace control by `-l plain-markdown`

[ancms2600]

I suggest everyone would benefit from this being the new plain-markdown.jst template going forward:

<%
for (const section of sections) {
    const docsText = section.docsText
        .replace(/^\s*(\/\*\*| \*\/| \* ?)/gm,'')
        .trim();

    if ('' !== docsText) { %><%=
        docsText
%>

<%
    }

    if ('' !== section.codeText.trim()) { %>
`%><%``js
<%=
        section.codeText
            .replace(/\s$/,'')
            .replace(/^(?:\s*[\r\n])+/,'')
            .replace(/(?:[\r\n]\s*)+$/,'')
%>
`%><%``

<%
    }
}
%>

Rationale:

• omits empty comments and code lines (above and below)
• removes extra padding above and below the code block areas, which looked accidental and annoying
• two lines of comments next to each other will become one line (a paragraph) in markdown rendering, but two lines with a line-break between will remain two lines in markdown rendering (two paragraphs). this was not happening before.

...and my language file, for anyone else who also likes to mix use JSDocs with Docco:

{
  ".js": {"name": "javascript", "symbol": "(//|/\\*\\*|\\*/|\\*)"}
}

For an example, I like to do my JSDocs like this, so they work in Markdown, as well as IDE:

    /**
     * ### _id(t)
     * Required by all MongoDB documents,
     * and is a type of `ObjectId` from its own collection.
     *
     * type + name | description
     * ---|---
     * @param {string} t - | Name of model.
     * @returns {object} - | Instance of validation rule.
     */
    COMMON_SCHEMA._id        = t => field().objectId(t);

Currently invoking like:

# Makefile
documentation:
    yarn global add diagrams docco
    docco -t "docs/_docco_template.jst" -L "docs/_docco_languages.json" -c "/dev/null" -o "docs/" "shared/public/models/schema.js" && \
    mv docs/shared/public/models/schema.html docs/schema.md && \
    rm -rf docs/shared docs/null

Sorry, was too lazy to fork and PR this.