Remove newlines inside & inbetween block-elements for better readability

[EvitanRelta]

Currently, the below HTML:

<blockquote forcehtml>
    <p>Line 1</p>
    <p>Line 2</p>
<pre><code>Codeblock
</code></pre>
    <h1>Heading</h1>
</blockquote>

is converted to:

<blockquote>
  <p>
    Line 1
  </p>
  
  <p>
    Line 2
  </p>
  
<pre><code>Codeblock
</code></pre>
  
  <h1>
    Heading
  </h1>
</blockquote>

which has alot of unnecessary newlines.

---

It would be nice to remove the newlines inbetween inner block-elements (eg. paragraphs/codeblocks/headings), as well as make each inner block-element take only 1 line, like so:

<blockquote>
  <p>Line 1</p>
  <p>Line 2</p>
<pre><code>Codeblock
</code></pre>
  <h1>Heading</h1>
</blockquote>

Note: The removal of newlines inbetween inner block-elements inside blockquotes can be achieved by passing down a boolean, which controls whether to add \n\n to end of the inner-content in each block-element-rule

---

Similarly, block-elements that has no attributes and contain 1 liner inner-content (ie. contains no \n), can be made into 1 liners to improve readability, like so:

<!-- Improved 1 liner -->
<p>TEXT</p>

<!-- Current multi-line block-elements -->
<p>
  TEXT
</p>

[EvitanRelta]

When prototyping the table conversion, I discovered that this HTML:

<table forcehtml>
  <thead>
    <tr>
      <th>h1</th>
      <th>h2</th>
      <th>h3</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>c1</td>
      <td>c1</td>
      <td>c3</td>
    </tr>
    </tr>
  </tbody>
</table>

which converted to this markdown:

<table>
  <tr>
    <th>
      h1
    </th>
    
    <th>
      h2
    </th>
    
    <th>
      h3
    </th>
  </tr>
  
  <tr>
    <td>
      c1
    </td>
    
    <td>
      c1
    </td>
    
    <td>
      c3
    </td>
  </tr>
</table>

incorrectly renders in GitHub as shown:

<th>
  h2
</th>

<th>
  h3
</th>

<td>
  c1
</td>

<td>
  c3
</td>

h1
c1

It can be fixed by at least removing the blank lines inbetween the inner <tr> / <th> / <td> tags:

<table>
  <tr>
    <th>
      h1
    </th>
    <th>
      h2
    </th>
    <th>
      h3
    </th>
  </tr>
  <tr>
    <td>
      c1
    </td>
    <td>
      c1
    </td>
    <td>
      c3
    </td>
  </tr>
</table>

Thus, this issue's label is being changed to bug.