Markdown Preview - No automatic hyperlink for python filenames with underscore

[grotewortel]

Issue Type: Bug

Reproduction:

1. Create a new markdown file
2. Create content:

file_name.py - this has no hyperlink

file-name.py - this has a hyperlink

3. Open preview

Expected behaviour: Both python files should have a hyperlink
Actual behaviour: The filename with the underscore does not have a hyperlink

Possibly _ is not part of the filename recognition algorith.

Please see screenshot for an example.

VS Code version: Code 1.56.1 (e713fe9, 2021-05-06T10:08:24.325Z)
OS version: Darwin x64 19.6.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz (12 x 2600)
GPU Status	2d_canvas: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	16.00GB (0.32GB free)
Process Argv	--disable-extensions
Screen Reader	no
VM	0%

Extensions disabled

[grotewortel]

[mjbvz]

This the default markdown-it linkifier behavior: https://markdown-it.github.io/#md3=%7B%22source%22%3A%22file_name.py%20-%20this%20has%20no%20hyperlink%5Cn%5Cnfile-name.py%20-%20this%20has%20a%20hyperlink%22%2C%22defaults%22%3A%7B%22html%22%3Afalse%2C%22xhtmlOut%22%3Afalse%2C%22breaks%22%3Afalse%2C%22langPrefix%22%3A%22language-%22%2C%22linkify%22%3Atrue%2C%22typographer%22%3Atrue%2C%22_highlight%22%3Atrue%2C%22_strict%22%3Afalse%2C%22_view%22%3A%22html%22%7D%7D

You can set "markdown.preview.linkify": false to disable automatic link creation