Create a link to Threshold's brand assets

[Luna5-threshold]

Threshold Network's brand assets currently reside in our Notion, however, we need to provide a link to them in our official page.

Please include a link to our brand assets within our website -> https://www.notion.so/thresholdnetwork/06ca766fc2cd402ab99bfe952a41c5af?v=a2e40d1427d54cfd8c48ea0c9ab9e7dd&pvs=4

[liz-shinn]

@r-czajkowski & @michalsmiarowski

We have a design for this that adds a page to the website Brand Assets. On this page, there is downloadable assets & design documentation on the Threshold website. I will create a ticket for it. https://github.com/threshold-network/splash-page/issues/82

Since we likely won't have bandwidth to tackle those designs this sprint, in the meantime let's add a link like Luna requests above.

Here's the design adding the "Brand Assets" external link: https://thresholdnetwork.notion.site/06ca766fc2cd402ab99bfe952a41c5af

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