fixes #18113

Fixes #18069

**Bug**
Script and style blocks inside markdown cannot contain blank lines

**fix**
Add a specific rule for script, style, and pre blocks according to the common mark spec: http://spec.commonmark.org/0.27/#html-block

fixes #18017

Add F4 shortcut for navigating search results

Improve edit action and search in Settings editor

fixes #17113

Update copyright year to 2017

Sequentialise writes to files

Expose navigator methods so I can avoid calling selectNext multiple times per action- it has side effects

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