fixes "Attribute Qt::AA_EnableHighDpiScaling must be set before
QCoreApplication is created."

Update to mtxclient 0.3.0

This reverts commit 4b807229.

User can now select a font from the installed fonts on their system

This font currently will only be applied when nheko is restarted
(similar to how font size and scaling currently work).  This will
be addressed in a future commit.  Additionally, the dropdown
does not correctly select the previously-chosen user font, and
instead defaults to the first font available on the system
(alphabetically).  This is similar to the issue with the 'Theme'
combo defaulting to 'Light' even when another theme is selected.

fixes #161

fixes #79

fixes #397

fixes #357
fixes #335
fixes #230

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- Patch the olm repo with a CMakeLists.txt file

fixes #141

The color scheme of nheko obeys the default color theme of Qt
(i.e. the system theme). It uses a Qt stylesheet to accomplish this,
which means replacing the color theme with a custom theme would only
be a matter of writing a new style sheet and loading it into the app.