Highlight escaped characters in default Light+ (Fix #48638)

[Ikuyadeu]

Fixed #48638
Before

After

These issue is cause of string and constant.character.escape is same(#a31515).

This new color(#800000) looks not so changed. I referenced dark-theme
https://github.com/Microsoft/vscode/blob/master/extensions/theme-defaults/themes/dark_plus.json#L159
use same color from
https://github.com/Microsoft/vscode/blob/master/extensions/theme-defaults/themes/dark_vs.json#L90
and
https://github.com/Microsoft/vscode/blob/master/extensions/theme-defaults/themes/dark_vs.json#L164

So this #800000 is used from
https://github.com/Microsoft/vscode/blob/master/extensions/theme-defaults/themes/light_vs.json#L88
and
https://github.com/Microsoft/vscode/blob/master/extensions/theme-defaults/themes/light_vs.json#L66

[mjbvz]

Code change looks good but the color is too low contrast. What about #ff0000 which is used by the light theme for regular expressions?

[Ikuyadeu]

@mjbvz Thank you for review!
I fixed to #ff0000 that from keyword.operator.or.regexp and keyword.control.anchor.regexp

However, #000000 that from keyword.operator.quantifier.regexp is also good contrast and it is same usage of default dark theme. Which is good for you?

Ps. Sorry I committed wrong version too, so I pushed one fixed commit too.

[mjbvz]

Thanks. If anyone complains about the bright red color, we can switch it to black as you suggest.

It's too late to put this change in the upcoming VS Code 1.23 release, but it will be in May VS Code release: 1.24

[Ikuyadeu]

@mjbvz OK, thank you for merge.