The instructions on adding Salesforce Lightning Design System's icons aren't clear to me, or just doesn't work for me. In my template I'm trying to use an example icon:

<svg aria-hidden="true" class="slds-icon" title="when needed">
  <use xlink:href="/assets/icons/standard-sprite/svg/symbols.svg#case"></use>
</svg>

and I also downloaded the icon's package and included it in the assets folder, so that the path to the svg is correct. When I try to push that change, I'm receiving the following console error:

ERROR running force:source:push:  Unexpected file found in package directory

The instructions on adding Salesforce Lightning Design System's icons aren't clear to me, or just doesn't work for me. In my template I'm trying to use an example icon:

<svg aria-hidden="true" class="slds-icon" title="when needed">
  <use xlink:href="/assets/icons/standard-sprite/svg/symbols.svg#case"></use>
</svg>

and I also downloaded the icon's package and included it in the assets folder, so that the path to the svg is correct. When I try to push that change, I'm receiving the following console error:

ERROR running force:source:push:  Unexpected file found in package directory