mdi-gold-add and mdi-gold-remove

[imLudwig]

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• I have searched all issues to make sure there isn't a request for this icon.
• I have searched the current library to make sure the icon doesn't already exist.
• I understand that brand icons are no longer being added and I can use SimpleIcons for my brand icon needs.
• I have followed the Material guidelines for system icons.

Tell us about your contribution.

I am building menus for in-game administration and noticed there are no gold-plus or gold-minus icons. Since gold already exists in MDI, I created these variants to maintain a consistent visual style.

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Upload the icon source.

gold-plus:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
  <title>gold-plus</title>
  <path d="M1 22L2.5 17H9.5L11 22H1
           M13 22L14.5 17H21.5L23 22H13
           M6 15L7.5 10H14.5L16 15H6
           M22 5V6H19V9H18V6H15V5H18V2H19V5Z"/>
</svg>

M 1 22 L 2.5 17 H 9.5 L 11 22 H 1 M 13 22 L 14.5 17 H 21.5 L 23 22 H 13 M 6 15 L 7.5 10 H 14.5 L 16 15 H 6 M 22 5 L 22 6 L 19 6 L 19 9 L 18 9 L 18 6 L 15 6 L 15 5 L 18 5 L 18 2 L 19 2 L 19 5 Z

gold-minus:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
  <title>gold-minus</title>
  <path d="M1 22L2.5 17H9.5L11 22H1
           M13 22L14.5 17H21.5L23 22H13
           M6 15L7.5 10H14.5L16 15H6
           M15 5H22V6H15Z"/>
</svg>

M 1 22 L 2.5 17 H 9.5 L 11 22 H 1 M 13 22 L 14.5 17 H 21.5 L 23 22 H 13 M 6 15 L 7.5 10 H 14.5 L 16 15 H 6 M 22 5 L 22 6 L 19 6 L 18 6 L 15 6 L 15 5 L 18 5 L 19 5 Z