bug in markdown syntax when line break included in emphasis

[18kimn]

Issue Type: Bug

*this whole sentence
should have italic formatting in vscode*

_this sentence 
should have it too_

**and this sentence should
be bolded**

But currently they show as regular text, and only when the entire string is placed on the same line does the formatting show up.

Here's a commonmark link showing that this works, and two examples in the spec that have this formatting: one two

Github supports it too, so you could try it out on a comment.

Not a huge issue of course, since most parsers seem to support this syntax, but just nice to have editor highlighting for it too :)

VS Code version: VSCodium 1.62.3 (ee8c7de, 2021-10-08T22:09:41.030Z)
OS version: Linux x64 5.11.0-43-generic
Restricted Mode: No

System Info

Item	Value
CPUs	11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz (8 x 2400)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: enabled_on rasterization: disabled_software skia_renderer: enabled_on video_decode: disabled_software vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	1, 1, 1
Memory (System)	15.36GB (0.53GB free)
Process Argv	--unity-launch
Screen Reader	no
VM	0%
DESKTOP_SESSION	plasma
XDG_CURRENT_DESKTOP	KDE
XDG_SESSION_DESKTOP	KDE
XDG_SESSION_TYPE	x11

Extensions (22)

Extension	Author (truncated)	Version
css-theme-completions	con	0.0.4
vscode-markdownlint	Dav	0.45.0
vscode-eslint	dba	2.2.2
gitlens	eam	11.7.0
prettier-vscode	esb	9.0.0
shell-format	fox	7.1.1
gc-excelviewer	Gra	4.0.45
r	Iku	2.3.4
path-autocomplete	ion	1.17.1
latex-workshop	Jam	8.22.0
vscode-edit-csv	jan	0.6.4
svg	joc	1.4.1
volar	joh	0.29.5
zotero	mbl	0.1.10
vscode-docker	ms-	1.18.0
vsliveshare	ms-	1.0.2902
color-highlight	nau	2.5.0
nebula-oni-theme	psu	1.4.0
marky-stats	rob	0.7.0
mdx	sil	0.1.0
svelte-vscode	sve	105.7.0
vscode-icons	vsc	11.8.0

(3 theme extensions excluded)

[mjbvz]

Duplicate of microsoft/vscode-markdown-tm-grammar#36