editorconfig: Use 4 spaces identation for Markdown files

This is because mkdocs doesn't render numbered lists correctly if they
have more than one paragraph using less than 4 spaces indentation.

For example, this:

```md
1. A list item.

   This list item gets improperly rendered.
```

Gets rendered like this in HTML:

```html
<ol>
<li><p>A list item./<p></li>
</o>
<p>This list item gets improperly rendered.</p>
```

While this:

```md
1. A list item.

    This list item gets improperly rendered.
```

Gets rendered like this in HTML:

```html
<ol>
<li>
<p>A list item.</p>
<p>This list item gets improperly rendered.</p>
</li>
</o>
```

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

.editorconfig

@@ -15,12 +15,9 @@ indent_style = space
 trim_trailing_whitespace = true
 
 # 4 space indentation
-[*.{py,pyi}]
+[*.{md,py,pyi}]
 indent_size = 4
 
 # 2 space indentation
 [{.editorconfig,CODEOWNERS,LICENSE,*.{in,json,proto,toml,yaml,yml}}]
 indent_size = 2
-
-# No indentation size specified for *.md because different blocks have
-# different indentation rules