add svg logo for ibc-go for top left corner and svg text for footer

[crodriguezvega]

Closes:

Related:

Description

This adds the SVG logo of IBC, so that it can be shown on the left side bar at the top.
It also adds an SVG with the text "cosmos" to be shown on the footer of the ibc-go docs site.

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For contributor use:

• Linked to relevant Github issues
• Provided a description
• Added a relevant changelog
• Re-reviewed Files changed

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For admin use:

• Checked errors / warnings on console
• Ran npm run build in the local dev repo to make sure it compiles without any errors
• When bumping version, made sure package-lock.json has the latest version