pidgin/pidgin

Use the id property of PurpleUiInfo as the directory name to use with XDG_CONFIG_HOME

Testing Done:
Ran both finch and pidgin.
Verified that they created `build/config/finch3` and `build/config/pidgin3` when run from a devenv environment.
Also verified that `gtk-gaim.ini` in `build/config/pidgin3` was no named `build/config/pidgin3/pidgin3.ini`.

Reviewed at https://reviews.imfreedom.org/r/1824/
---
id: im.pidgin.Finch3
runtime: org.gnome.Platform
runtime-version: '3.36'
sdk: org.gnome.Sdk
command: finch3
finish-args:
- --share=ipc
- --socket=x11
- --share=network
- --talk-name=org.freedesktop.Notifications
- --system-talk-name=org.freedesktop.Avahi
modules:
- packaging/flatpak/libpurple-common.yml
- packaging/flatpak/libgnt.yml
- name: finch3
buildsystem: meson
config-opts:
- -Dgtkui=false
- -Ddoc=false
sources:
- type: dir
path: '.'