Currently host_permissions is used for simplified permissions but this requests too broad permissions on installation. With some experimentation this might be able to be narrowed,
"host_permissions": [
"*://*.retrotxt.com/*",
"https://*/",
"http://*/",
"file://*/"
],

Currently
host_permissionsis used for simplified permissions but this requests too broad permissions on installation. With some experimentation this might be able to be narrowed,Viewing warnings