use AyatanaAppIndicator3 if available, fallback to AppIndicator3

[thinkmassive]

Description

Debian has transitioned to Ayatana Indicators:
https://wiki.debian.org/Ayatana/IndicatorsTransition

This allows pulsemeeter to support both libraries, so it can run on newer debian systems using default apt packages.

Fixes #66

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update (in the wiki)

In some newer distrobutions you may have to install this package (#66):
gir1.2-ayatanaappindicator3-0.1

sudo apt install gir1.2-appindicator3-0.1 gir1.2-ayatanaappindicator3-0.1

How Has This Been Tested?

Pulsemeeter is able to launch on Debian 12 with only standard system packages installed. I am unable to test falling back to the legacy AppIndicator3 library provided by gir1.2-appindicator3-0.1.

• Debian 12.7
• Linux 6.1.0-26-amd64
• Python 3.11.2

Checklist :

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

[thinkmassive]

My apologies, this is a duplicate of:

• Port to AyatanaAppindicator3 with backwards compatability for Appindi… #117