VSCode Markdown Code blocks Assembly Syntax highlighting

This extension adds Assembly syntax highlighting to Markdown fenced code blocks.

Code blocks like the following:

```asm
main:
        mov eax, 0xDEADCAFE
        int 3
```

will be highlighted, like:

This work based on Matt Bierner's work.

Setup

This extension does not add the grammar; it only connects Markdown ASM code blocks to the existing ASM grammar.

For this reason, it requires a preexisting extension that provides the grammar, for example, nasm x86 syntax highlighting.

Integration notes

When integrating into an existing project, a new language id entry needs to be added; if an existing one is recycled, the grammar will apply only to the new scope.

See PR on ASM Code Lens.