YAML syntax highlight is wrong on keys that happen to be keywords

[leafac]

Issue Type: Bug

The keys are highlighted as keywords, for example, consider the keyword on:

on: push
all: Are
other: highlighted
keys: differently

(For example, you may see the on keyword as a key in the configuration for a GitHub Action.)

Possibly related issued:

• Wrong YAML syntax highlighting #69171
• YAML incorrect highlighting #82300
• Incorrect highlighting when colon is used inside yaml literal style textmate/yaml.tmbundle#17

VS Code version: Code 1.44.0 (2aae1f2, 2020-04-08T08:23:56.137Z)
OS version: Darwin x64 19.4.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz (4 x 2300)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	8.00GB (0.56GB free)
Process Argv
Screen Reader	no
VM	0%

Extensions (5)

Extension	Author (truncated)	Version
githistory	don	0.6.3
prettier-vscode	esb	4.1.1
latex-workshop	Jam	8.8.0
code-spell-checker	str	1.8.0
code-spell-checker-portuguese	str	0.1.2

[alexr00]

Moved to the repo we get our yaml grammar from.