Suggestion on default font size ; playing nice with dark theme

[orionlee]

Two separate UI issues, but potential fixes are loosely related so I group them together.

1. The default font size seems to be a bit too large.
2. When Visual Studio Code is in a dark theme, the font color is not switched to light color.

For font size, it could be helpful if it can be specified by users. Another option is to obey Visual Studio Code's default size.

---

Suggested solution:

One way is to tweak the css:

vscode-markdown-editor/media-src/src/main.css

Lines 18 to 21 in aefdc13

	/* fix font family */
	.vditor .vditor-reset {
	font-family: var(--vscode-editor-font-family)!important;
	}

If we add the following to the css rule, it'll make the editor area use vscode' default color / font size (rather than the hardcode value in .vditor style)

    font-size: var(--vscode-font-size, var(--theme-font-size));
    color: var(--vscode-editor-foreground, var(--theme-foreground));    

With the css change, it looks like:

[jamesoflol]

Yeah the font is quite large for me - macos

[maolike]

大佬 快点改了发个版本呀 @zaaack