Markdown documents preview is broken

[StanKirilov]

Issue Type: Bug

Repro

1. Start latest version of Visual Studio Code
2. Open Markdown file
3. Click (or open task) to either Preview as side or full view

Expected
New or split window is opened with the rendered preview of the Markdown document

Observed
Bland new or split window is opened and nothing is render. The VS code shows the following message:

Error loading webview: Error: Could not register service workers: TypeError: Failed to register a ServiceWorker for scope ('vscode-webview://8f7e3023-2ed4-4a8e-9947-fec591011dad/') with script ('vscode-webview://8f7e3023-2ed4-4a8e-9947-fec591011dad/service-worker.js?platform=electron&id=8f7e3023-2ed4-4a8e-9947-fec591011dad&vscode-resource-origin=https%3A%2F%2F8f7e3023-2ed4-4a8e-9947-fec591011dad.vscode-webview-test.com'): ServiceWorker cannot be started.

Restarting the VS code or rebooting the PC doesn't help - the issue repro 100%

VS Code version: Code 1.56.0 (cfa2e21, 2021-05-04T22:09:06.405Z)
OS version: Windows_NT x64 10.0.19042

System Info

Item	Value
CPUs	Intel(R) Xeon(R) Gold 6248 CPU @ 2.50GHz (40 x 2494)
GPU Status	2d_canvas: unavailable_software gpu_compositing: disabled_software multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: disabled_off rasterization: disabled_software skia_renderer: enabled_on video_decode: disabled_software vulkan: disabled_off webgl: unavailable_software webgl2: unavailable_software
Load (avg)	undefined
Memory (System)	240.00GB (229.91GB free)
Process Argv	--crash-reporter-id 0a512a6f-e668-4785-ae2e-2bb3b02f451f
Screen Reader	no
VM	0%

Extensions (54)

Extension	Author (truncated)	Version
Bookmarks	ale	13.0.4
markdown-mermaid	bie	1.9.2
LinkCheckMD	bla	0.3.1
doxdocgen	csc	1.2.2
vscode-markdownlint	Dav	0.40.4
docs-article-templates	doc	0.2.11
docs-authoring-pack	doc	0.1.13
docs-build	doc	0.3.4
docs-images	doc	0.0.9
docs-linting	doc	0.0.7
docs-markdown	doc	0.2.89
docs-metadata	doc	1.0.6
docs-preview	doc	0.3.57
docs-scaffolding	doc	0.0.7
docs-yaml	doc	0.2.6
xml	Dot	2.5.1
gitlens	eam	11.4.1
vscode-codeql	Git	1.4.8
vscode-pull-request-github	Git	0.26.0
vscode-test-explorer	hbe	2.19.6
plantuml	jeb	2.14.5
better-cpp-syntax	jef	1.15.5
vscode-peacock	joh	3.9.1
chat	kar	0.35.0
rust-analyzer	mat	0.2.583
vscode-azurevirtualmachines	ms-	0.3.0
vscode-logicapps	ms-	1.0.11
extension-manifest-editor	ms-	0.1.5
csharp	ms-	1.23.11
mssql	ms-	1.10.1
python	ms-	2021.4.765268190
vscode-pylance	ms-	2021.5.1
jupyter	ms-	2021.6.811652604
remote-containers	ms-	0.177.0
remote-ssh	ms-	0.65.4
remote-ssh-edit	ms-	0.65.4
remote-wsl	ms-	0.56.1
vscode-remote-extensionpack	ms-	0.20.0
azure-account	ms-	0.9.8
azurecli	ms-	0.5.0
cmake-tools	ms-	1.7.2
cpptools	ms-	1.3.1
cpptools-extension-pack	ms-	1.0.0
mono-debug	ms-	0.16.2
powershell	ms-	2021.2.2
vsliveshare	ms-	1.0.4131
vsliveshare-audio	ms-	0.1.91
vsliveshare-pack	ms-	0.4.0
debugger-for-edge	msj	1.0.15
vscode-yaml	red	0.18.0
code-spell-checker	str	1.10.2
cmake	twx	0.0.17
vscodeintellicode	Vis	1.2.13
vscode-arduino	vsc	0.4.2

(1 theme extensions excluded)

A/B Experiments

vsins829:30139715
vsliv368:30146709
vsreu685:30147344
vspor879:30202332
vspor708:30202333
vspor363:30204092
vspre833cf:30267465
vshan820:30294714
vscus158:30286553

[mjbvz]

Duplicate of #122951