Sequentialise writes to files

with the arrow keys - partially address Microsoft/vscode#17324 but also will add a keyboard shortcut

* Improve Markdown code block tokens

Code blocks without a language weren't tokenized.
Code blocks didn't have their ending ``` punctuation tokenized.
Code blocks used to only have one token. Now each block has the following tokens available for syntax highlighters:
- Starting and ending ``` punctuations
- Code block's language setting
- Code snippet

* Variable whitespace for MD code block ``` token

Allow for variable amount of whitespacing before ``` code blocks

* Reorder raw blocks

Raw blocks were preventing tokenizing as languaged blocks. Putting them on bottom resolves this.

* Fix MD block detection when following paragraph

Used to require a new line inbetween ``` code blocks and preceding paragraph text.

* Prevent broken language grammar leaks in MD fences

Prevents leaks in MD code fences while also capturing the closing fence punctuations.

* Update Markdown tokenizer test file

fixes #18016

This reverts commit 58ab5ecd.

Check window.autoDetectHighContrast on window load

Some debt and feature work

linux argument startup fix

This reverts commit bc46e789.

It was never removed and many people rely on it with keybindings such as:
{ "key": "ctrl+`",          "command": "workbench.action.terminal.focus", "when": "!terminalFocus" }

The whole file name is used when dealing with filename associations