contributor table icons: set fix widths
contributor table icons: set fix widths

fixes #281

noplanman/podlove-publisher,podlove/podlove-publisher,katrinleinweber/podlove-publisher,katrinleinweber/podlove-publisher,noplanman/podlove-publisher,noplanman/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,noplanman/podlove-publisher,katrinleinweber/podlove-publisher,noplanman/podlove-publisher,katrinleinweber/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,katrinleinweber/podlove-publisher