Introduce the font-display descriptor for custom fonts used in HubSpot Widgets

Since HubSpot is using two custom fonts (at least in my chat widget): I propose HubSpot developers should add the `font-display` descriptor to the font declaration in the CSS. This can potentially save up to 100 ms of loading time and would potentially increase customers' google ranking when they are using the HubSpot widgets on their webpages.


While the browser support is currently only at around 80% (see caniuseCSS-Tricks states, that "[...] If other browsers don't support it, they will behave according to their defaults. This isn't necessarily bad in that it doesn't break anything, [...]".