Revisit find match and word highlight colors

[svipas]

While I was working on #10 fix I noticed that highlighting for find match and words aren't good and hard to see. I checked VS Code's dark theme and GitHub theme and they are doing better job.

Keys:

      "editor.findMatchBackground": "#ff0000",
      "editor.findMatchHighlightBackground": "#ff0000",
      "searchEditor.findMatchBackground": "#ff0000",
      "editorOverviewRuler.findMatchForeground": "#ff0000",
      "editor.wordHighlightBackground": "#ff0000",
      "editor.wordHighlightStrongBackground": "#ff0000",
      "editor.wordHighlightTextBackground": "#ff0000",
      "editorOverviewRuler.wordHighlightForeground": "#ff0000",
      "editorOverviewRuler.wordHighlightStrongForeground": "#ff0000",
      "editorOverviewRuler.wordHighlightTextForeground": "#ff0000"
     // Also, there are borders, but they look weird - we should use it only in case if there's no way to fix it properly

I tried to fix it, but it isn't so easy, because it's hard to find color + opacity which matches theme colors and looks easy to read. So for now let's keep this issue open as a tracker.