docs(get-started): add Dwellir to Builder Stack

[benjichat]

What changed? Why?

Adds Dwellir to the Stack Partners table on the Builder Stack page. Dwellir runs archive RPC nodes for Base Mainnet and Base Sepolia. The offer for Base builders is one month free on the Developer or Growth plan with promo code BASEBUILDER.

This replaces #169, which added Dwellir to the old node providers page. That page was removed in #1772.

Notes to reviewers

One new row, placed alphabetically between Definitive Finance and Dune. We are submitting the Builder Stack service provider form for this offer as well.

How has it been tested?

node scripts/lint-mdx.js docs/get-started/builder-stack.mdx passes. Endpoint: https://api-base-mainnet-archive.n.dwellir.com/

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[cb-heimdall]

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