Regarding "keychain support is disabled on Linux" in shim.ts

Hello,

When I read shim.ts to search for the reason of my problem of IPv4 address is used instead of IPv6 one, saw the following comment on the reason of keychain is disabled in Linux.

// For now, keychain support is disabled on Linux because when
// keytar is loaded it seems to cause the following error when
// loading Sharp:
//
// Something went wrong installing the "sharp" module
// /lib/x86_64-linux-gnu/libz.so.1: version `ZLIB_1.2.9' not found
// (required by
// /home/travis/build/laurent22/joplin/packages/app-cli/node_modules/sharp/build/Release/../../vendor/lib/libpng16.so.16)

Then, I searched Google with the error message, and found a thread "Electron beta appears to use system zlib, can conflict with sharp #892" regarding this problem.

Although I am very unsure that the thread will solve your problem, but hope so.

In addition, if the error occurs in installing sharp module just like "npm install sharp", the error did not occur on my environment (Linux Mint 20, node v14.15.1, npm 6.4.18).

But again, I'm not sure this is right or not because I'm just a npm user (no experience with programming with it).

Sorry for uncertain info.