Fixed typo on package.yml from pkconfig(Qt6Core) to pkgconfig(Qt6Core)

Add pkgconfig(Qt6Core) to build deps

Removed install -Dm00644 out/Release/libffmpeg.so $installdir/usr/share/opera/libffmpeg.so from package.yml

@Staudey I built successfully without that in there, but Opera wouldn't launch. I didn't grab the exact error message from the terminal, but it referenced /usr/lib/opera/libffmpeg.so, so I added it back as an install path.

Change package.yml as requested

Add pkgconfig(Qt5Core)

Okay, tested against Lenovo w/newer AMD, 2014 dual core Intel/HP, and 7th gen Intel/Nvidia combo. Mailspring runs fine on all my configurations.

Mailspring 1.10.3-41 has no issues on my laptop. What hardware are you using?

Updated MAINTAINERS file

1. Updating D13110: Update opera-stable to 85.0.4341.60 #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

Removed builddep pkgconfig(pangocairo)