New Text for Cosigner

_Cosigner doesn't seem to currently have a central "About". I'd suggest adding the following, linked from a small version of the app-icon in the middle of the top bar, just as with QR Tool:_

> Gordian Cosigner is open-source software that is a project of Blockchain Commons. It was created to allow the offline signing of Bitcoin transactions using keys and accounts stored in Gordian Cosigner. It is simply a utility: it imports PSBTs as text, file, or QR, and then will sign and export that PSBT. A wallet or full node is required to generate and to send the PSBTs. Click the info buttons on the Cosigners, Accounts, and Payments tabs for more information on how Gordian Cosigner works.

> Gordian Cosigner demonstrates the Gordian principles. It allows you sign PSBTs as you see fit (independence), keeps that signing offline (privacy), keeps your seeds offline (resilience), and communicates via QRs and URs (openness).

> Creating reference applications of this sort supports the goals of Blockchain Commons, to enable responsible key management and to support self-sovereign solutions. Blockchain Commons is a "not-for-profit" social benefit corp committed to open source and open development.

> [Visit Our Support] -> https://github.com/BlockchainCommons/Gordian/discussions

> [Visit the Repo] -> https://github.com/BlockchainCommons/GordianCosigner-iOS

> [Visit Our Website] -> https://www.blockchaincommons.com/

_For the **Cosigners** tab, info:_

Cut the subsclause "seeds and other" in the last sentence, since there no longer seems to be a differentiation between seeds and other cosigners.

_For the **Accounts** tab, info:_

Similarly, delete "(including the seeds from your seeds tab, which you will be using to sign)" as there's no longer a seeds tab. (I assume that's now all on the Cosigners tab?)