docs(topics): Add Bitrefill topic page

data/topics/bitrefill.mdx

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+---
+title: 'Bitrefill'
+summary: 'A commercial service for buying gift cards, eSIMs, and mobile top-ups with bitcoin and Lightning, with Thor, a product that opens inbound Lightning channels on demand.'
+ogSummary: 'A commercial service for buying gift cards, eSIMs, and mobile top-ups with bitcoin and Lightning.'
+category: 'Lightning'
+aliases: ['Thor']
+---
+
+[Bitrefill](https://www.bitrefill.com) is a commercial service that lets users buy gift cards, eSIMs, and mobile top-ups with bitcoin, paying on-chain or over the [Lightning Network](/topics/lightning). A user selects a brand, pays in bitcoin, and receives a digital code instantly; no fiat conversion required. The service covers thousands of brands in almost every corner of the world. 
+
+Alongside the gift card store, Bitrefill offers a channel-opening service for Lightning, named [Thor](https://www.bitrefill.com/thor-lightning-network-channels/). A user purchases a channel from Bitrefill's node, at any capacity between 300,000 and 16,000,000 sats, and Bitrefill funds it and holds it open for 30 days. This solves the inbound liquidity problem for new Lightning nodes: the recipient can start accepting Lightning payments right away, without needing another node to open a channel to them first.
+
+Bitrefill launched in 2014, founded by Sergej Kotliar in Stockholm, and added Lightning payments in early 2018 among the first commercial merchants on mainnet. Bitrefill is a custodial service, where users trust the company to deliver goods after payment. Thor channels are temporary, closing after 30 days unless activity extends them. 
+
+## References
+
+- [bitrefill.com](https://www.bitrefill.com/)
+- [Thor, Lightning channel service](https://www.bitrefill.com/thor-lightning-network-channels/)