[MonacoPreviewHandler][Settings] Resolve preview handler race (#16180)

* Register .markdown with the correct handler

* Fix spelling

* Move file name extensions from "expect.txt" to "excludes.txt"

* Revert "Move file name extensions from "expect.txt" to "excludes.txt""

This reverts commit 710d5a4968.
I must have misunderstood the instructions.

* Revert "Register .markdown with the correct handler"

This reverts commit 5c37b009f3.

* Work in progress

* Code ready for testing

* Update excludes.txt

* Update excludes.txt

* Update modulesRegistry.h

* Update modulesRegistry.h

For the want of an exclamation mark, a kingdom is lost!

* Update modulesRegistry.h

* Work on modulesRegistry.h per code review in 16180

Removed all previous exclusions from Monaco preview handler. Added a new exclusion: SVGZ. It's a binary file that Monaco cannot, in any meaningful way, read.

* Update expect.txt

* Update accessory files

* Disable machine-wide checks for performance reasons

.github/actions/spell-check/excludes.txt

@@ -46,6 +46,7 @@ ignore$
 ^src/modules/previewpane/PreviewPaneUnitTests/HelperFiles/MarkdownWithHTMLImageTag\.txt$
 ^src/modules/previewpane/UnitTests-MarkdownPreviewHandler/HelperFiles/MarkdownWithHTMLImageTag.txt$
 ^tools/CleanUp_tool/CleanUp_tool\.vcxproj\.filters$
+^tools/Verification scripts/Check preview handler registration\.ps1$
 ^\.github/
 ^\.github/actions/spell-check/
 ^\.gitmodules$

.github/actions/spell-check/expect.txt

@@ -1179,6 +1179,9 @@ MAXIMIZEBOX
 MAXSHORTCUTSIZE
 maxversiontested
 MBs
+mdtext
+mdtxt
+mdwn
 MBUTTON
 MBUTTONDBLCLK
 MBUTTONDOWN
@@ -1225,6 +1228,8 @@ Miracast
 mirophone
 Mishkeegogamang
 mjpg
+mkd
+mkdn
 mlcfg
 MMDDYYYY
 mmdeviceapi
@@ -1961,6 +1966,7 @@ SVE
 SVGIn
 SVGIO
 svgpreviewhandler
+svgz
 SWC
 SWFO
 SWP