Feature Request: Custom IPFS Gateway

### **Description**
Allow me to add a custom IPFS Gateway.

### **Technical Details**
The IPFS Gateway drop-down should have an option for "Custom" that would allow me to put in an IPFS Gateway of my own.

### **Acceptance Criteria**
I am able to use my personal IPFS Gateway.

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The whole point of IPFS is that it allows for trustless web browsing. By not forcing me to use a third party IPFS gateway, it largely defeats the purpose of the whole platform. While it is better than nothing, it goes against the ethos of censorship resistance.

Start by locating the IPFS Gateway drop-down in the mobile browser and reading how the existing gateway choices are selected and used. Check the related browsing flow to understand where a custom value must be passed. Done means a user can choose Custom, enter a personal IPFS Gateway, and browse through it.

Written by the indexing model from the issue text.