The link handler's window starts with an app's minimal environment, and only PATH, the config locations and XDG_CONFIG_HOME/XDG_STATE_HOME were carried into it. With XDG_CACHE_HOME or XDG_RUNTIME_DIR set, lazysecrets opened from a link used another cache file and didn't see running instances' sockets; on Linux, without XDG_DATA_HOME it looked for its desktop entry in the wrong place. `handler install` now records those three too: run it again to pick them up.
Reviewed-on: #71
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>
keb