add markdown primer for gui notes onlineHelp

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

markdown-primer.adoc

@@ -0,0 +1,174 @@
+Markdown Primer
+===============
+
+[quote, John Gruber, https://daringfireball.net/projects/markdown/]
+____
+Markdown is a text-to-HTML conversion tool for web writers. Markdown allows you
+to write using an easy-to-read, easy-to-write plain text format, then convert
+it to structurally valid XHTML (or HTML).
+____
+
+The {pve} web-interface has support for using Markdown to rendering rich text
+formatting in node and virtual guest notes.
+
+{pve} supports CommonMark with most extensions of GFM (GitHub Flavoured Markdown),
+like tables or task-lists.
+
+[[markdown_basics]]
+
+Markdown Basics
+---------------
+
+Note that we only describe the basics here, please search the web for more
+extensive resources, for example on https://www.markdownguide.org/
+
+Headings
+~~~~~~~~
+
+----
+# This is a Heading h1
+## This is a Heading h2 
+##### This is a Heading h5
+----
+
+
+Emphasis
+~~~~~~~~
+
+Use `*text*` or `_text_` for emphasis.
+
+Use `**text**` or `__text__` for bold, heavy-weight text.
+
+Combinations are also possible, for example:
+
+----
+_You **can** combine them_
+----
+
+Links
+~~~~~
+
+You can use automatic detection of links, for example,
+`https://forum.proxmox.com/` would transform it into a clickable link.
+
+You can also control the link text, for example:
+
+----
+Now, [the part in brackets will be the link text](https://forum.proxmox.com/).
+----
+
+Lists
+~~~~~
+
+Unordered Lists
+^^^^^^^^^^^^^^^
+
+Use `*` or `-` for unordered lists, for example:
+
+----
+* Item 1
+* Item 2
+* Item 2a
+* Item 2b
+----
+
+Adding an indentation can be used to created nested lists.
+
+Ordered Lists
+^^^^^^^^^^^^^
+
+----
+1. Item 1
+1. Item 2
+1. Item 3
+  1. Item 3a
+  1. Item 3b
+----
+
+NOTE: The integer of ordered lists does not need to be correct, they will be numbered automatically.
+
+Task Lists
+^^^^^^^^^^
+
+Task list use a empty box `[ ]` for unfinished tasks and a box with an `X` for finished tasks.
+
+For example:
+
+----
+- [X] First task already done!
+- [X] Second one too
+- [ ] This one is still to-do
+- [ ] So is this one
+----
+
+Tables
+~~~~~~
+
+Tables use the pipe symbol `|` to separate columns, and `-` to separate the
+table header from the table body, in that separation one can also set the text
+alignment, making one column left-, center-, or right-aligned.
+
+----
+| Left columns  | Right columns |  Some  | More | Cols.| Centering Works Too
+| ------------- |--------------:|--------|------|------|:------------------:|
+| left foo      | right foo     | First  | Row  | Here | >center<           |
+| left bar      | right bar     | Second | Row  | Here | 12345              |
+| left baz      | right baz     | Third  | Row  | Here | Test               |
+| left zab      | right zab     | Fourth | Row  | Here | ☁️☁️☁️              |
+| left rab      | right rab     | And    | Last | Here | The End            |
+----
+
+Note that you do not need to align the columns nicely with white space, but that makes
+editing tables easier.
+
+Block Quotes
+~~~~~~~~~~~~
+
+You can enter block quotes by prefixing a line with `>`, similar as in plain-text emails.
+
+----
+> Markdown is a lightweight markup language with plain-text-formatting syntax,
+> created in 2004 by John Gruber with Aaron Swartz.
+>
+>> Markdown is often used to format readme files, for writing messages in online discussion forums,
+>> and to create rich text using a plain text editor.
+----
+
+
+Code and Snippets
+~~~~~~~~~~~~~~~~~
+
+You can use backticks to avoid processing for a few word or paragraphs. That is useful for
+avoiding that a code or configuration hunk gets mistakenly interpreted as markdown.
+
+Inline code
+^^^^^^^^^^^
+
+Surrounding part of a line with single backticks allows to write code inline,
+for examples:
+
+----
+This hosts IP address is `10.0.0.1`.
+----
+
+Whole blocks of code
+^^^^^^^^^^^^^^^^^^^^
+
+For code blocks spanning several lines you can use triple-backticks to start
+and end such a block, for example:
+
+----
+```
+# This is the network config I want to remember here
+auto vmbr2
+iface vmbr2 inet static
+        address 10.0.0.1/24
+        bridge-ports ens20
+        bridge-stp off
+        bridge-fd 0
+        bridge-vlan-aware yes
+        bridge-vids 2-4094
+
+```
+----
+

pve-admin-guide.adoc

@@ -309,6 +309,9 @@ Firewall Macro Definitions
 
 include::pve-firewall-macros.adoc[]
 
+:leveloffset: 1
+[appendix]
+include::markdown-primer.adoc[]
 
 :leveloffset: 1
 [appendix]