Add support for mdv with $NB_MARKDOWN_TOOL.

refs gh-62

README.md

@@ -222,6 +222,7 @@ Also supported for various enhancements:
 [Lynx](https://en.wikipedia.org/wiki/Lynx_(web_browser)),
 [`mdcat`](https://github.com/swsnr/mdcat),
 [`mdless`](https://github.com/ttscoff/mdless),
+[`mdv`](https://github.com/axiros/terminal_markdown_viewer),
 [Midnight Commander (`mc`)](https://en.wikipedia.org/wiki/Midnight_Commander),
 [`mpg123`](https://en.wikipedia.org/wiki/Mpg123),
 [MPlayer](https://en.wikipedia.org/wiki/MPlayer),
@@ -1438,6 +1439,7 @@ Supported file types and tools include:
   - [`glow`](https://github.com/charmbracelet/glow)
   - [`mdcat`](https://github.com/swsnr/mdcat)
   - [`mdless`](https://github.com/ttscoff/mdless)
+  - [`mdv`](https://github.com/axiros/terminal_markdown_viewer)
 - PDF files:
   - [`termpdf.py`](https://github.com/dsanson/termpdf.py)
     with [kitty](https://sw.kovidgoyal.net/kitty/)
@@ -9521,7 +9523,7 @@ Example Values: '0', '1'
 ```text
 Default: '' (default pager)
 
-Supported Values: 'bat', 'glow', 'mdcat', 'mdless'
+Supported Values: 'bat', 'glow', 'mdcat', 'mdless', 'mdv'
 ```
 
 <p>

nb

@@ -18828,7 +18828,12 @@ Can't show archives. Export archive and expand to edit.\\n"
           cat "${_target_path}"
         } | {
           if _contains "${_target_extension:-}" "markdown" "md" &&
-             _contains "${NB_MARKDOWN_TOOL:-}" "bat" "glow" "mdcat" "mdless"
+             _contains "${NB_MARKDOWN_TOOL:-}" \
+               "bat" \
+               "glow" \
+               "mdcat" \
+               "mdless" \
+               "mdv"
           then
             if [[   "${NB_MARKDOWN_TOOL:-}" == "bat"    ]]
             then
@@ -18842,6 +18847,9 @@ Can't show archives. Export archive and expand to edit.\\n"
             elif [[ "${NB_MARKDOWN_TOOL:-}" == "mdless" ]]
             then
               mdless
+            elif [[ "${NB_MARKDOWN_TOOL:-}" == "mdv"    ]]
+            then
+              mdv "${_target_path}" | _pager
             fi
           else
             {