feat(design): add Stellar-focused hero and chains exploration (close issues)

[olalois]

This PR adds a Stellar-partner badge to the hero, emphasizes Stellar in the chains section, and includes design artifacts in /design.\n\nCloses #18\nCloses #19\nCloses #20\nCloses #21\nCloses #22\nCloses #23\nCloses #24\nCloses #25\nCloses #26\nCloses #27\nCloses #28\nCloses #29\nCloses #30\nCloses #31\nCloses #32\nCloses #33\nCloses #34\nCloses #35\nCloses #36\nCloses #37\nCloses #38\nCloses #39\nCloses #40

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[truthixify]

Heads up: I retargeted this from main to develop. For wave 6 all PRs land on develop first (we freeze on develop before merging to main). No action needed from you, just a heads-up. If you rebase in the future, base on origin/develop, not origin/main.