Added docs as asciidoctor with cross platform support. (#5733)

* Added docs as asciidoctor with cross platform support.

* Fixed release script with new doc building mechanism.

doc/api/embed_parameters.adoc

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+== Embed parameters
+You can easily embed your etherpad-lite into any webpage by using iframes. You can configure the embedded pad using embed parameters.
+
+Example:
+
+Cut and paste the following code into any webpage to embed a pad. The parameters below will hide the chat and the line numbers and will auto-focus on Line 4.
+
+[source, html]
+----
+<iframe src='http://pad.test.de/p/PAD_NAME#L4?showChat=false&showLineNumbers=false' width=600 height=400></iframe>
+----
+
+=== showLineNumbers
+ * Boolean
+
+Default: true
+
+=== showControls
+ * Boolean
+
+Default: true
+
+=== showChat
+ * Boolean
+
+Default: true
+
+=== useMonospaceFont
+ * Boolean
+
+Default: false
+
+=== userName
+ * String
+
+Default: "unnamed"
+
+Example: `userName=Etherpad%20User`
+
+=== userColor
+ * String (css hex color value)
+
+Default: randomly chosen by pad server
+
+Example: `userColor=%23ff9900`
+
+=== noColors
+ * Boolean
+
+Default: false
+
+=== alwaysShowChat
+ * Boolean
+
+Default: false
+
+=== lang
+ * String
+
+Default: en
+
+Example: `lang=ar` (translates the interface into Arabic)
+
+=== rtl
+ * Boolean
+
+Default: true
+Displays pad text from right to left.
+
+=== #L
+ * Int
+
+Default: 0
+Focuses pad at specific line number and places caret at beginning of this line
+Special note: Is not a URL parameter but instead of a Hash value
+