Do not modify header lines and trailing whitespaces

This is going to preserve line-ending of extracted header text as they
are provided by users. In other words we are going to always assume the
header text is formatted in the "intended" way by users. So we're never
going to modify line-endings and won't append `<SPACE><SPACE>` at the
end of paragraph lines.

Signed-off-by: Khosrow Moossavi <khos2ow@gmail.com>

docs/reference/asciidoc-document.md

@@ -64,7 +64,7 @@ generates the following output:
     - list item 1
     - list item 2
 
-    Even inline **formatting** in _here_ is possible.  
+    Even inline **formatting** in _here_ is possible.
     and some [link](https://domain.com/)
 
     * list item 3
@@ -87,7 +87,7 @@ generates the following output:
     }
     ```
 
-    Here is some trailing text after code block,  
+    Here is some trailing text after code block,
     followed by another line of text.
 
     | Name | Description     |

docs/reference/asciidoc-table.md

@@ -64,7 +64,7 @@ generates the following output:
     - list item 1
     - list item 2
 
-    Even inline **formatting** in _here_ is possible.  
+    Even inline **formatting** in _here_ is possible.
     and some [link](https://domain.com/)
 
     * list item 3
@@ -87,7 +87,7 @@ generates the following output:
     }
     ```
 
-    Here is some trailing text after code block,  
+    Here is some trailing text after code block,
     followed by another line of text.
 
     | Name | Description     |

docs/reference/markdown-document.md

@@ -65,7 +65,7 @@ generates the following output:
     - list item 1
     - list item 2
 
-    Even inline **formatting** in _here_ is possible.  
+    Even inline **formatting** in _here_ is possible.
     and some [link](https://domain.com/)
 
     * list item 3
@@ -88,7 +88,7 @@ generates the following output:
     }
     ```
 
-    Here is some trailing text after code block,  
+    Here is some trailing text after code block,
     followed by another line of text.
 
     | Name | Description     |

docs/reference/markdown-table.md

@@ -65,7 +65,7 @@ generates the following output:
     - list item 1
     - list item 2
 
-    Even inline **formatting** in _here_ is possible.  
+    Even inline **formatting** in _here_ is possible.
     and some [link](https://domain.com/)
 
     * list item 3
@@ -88,7 +88,7 @@ generates the following output:
     }
     ```
 
-    Here is some trailing text after code block,  
+    Here is some trailing text after code block,
     followed by another line of text.
 
     | Name | Description     |