feat: add steelseries arctis 7 plus (2021) support

[Michsior14]

This adds Steelseries Arctis 7 Plus support for side tone and inactive time (tested).
I couldn't find in wireshark any info regarding battery status so this is skipped for now. I would welcome help though in this matter.

Additionally this model support a few Equalizer presets (also custom settings) that I can successfully change via following commands:

# flat
./headsetcontrol --dev -- --device 0x1038:0x220e --interface 3 --send "0x0, 0x33, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 00"

# bass boost
./headsetcontrol --dev -- --device 0x1038:0x220e --interface 3 --send "0x0, 0x33, 0x1f, 0x20, 0x1a, 0x15, 0x15, 0x16, 0x16, 0x16, 0x16, 0x23, 00"

# smily
./headsetcontrol --dev -- --device 0x1038:0x220e --interface 3 --send "0x0, 0x33, 0x1e, 0x1b, 0x15, 0x10, 0x10, 0x13, 0x1b, 0x1e, 0x20, 0x1f, 00"

# focus
./headsetcontrol --dev -- --device 0x1038:0x220e --interface 3 --send "0x0, 0x33, 0x0e, 0x16, 0x11, 0x13, 0x20, 0x24, 0x1f, 0x11, 0x18, 0x11, 00"

I can add this to the project if you are interested in supporting EQ.

[Michsior14]

All format issues should be resolved now 😃

EDIT:
Not sure about whitespaces workflow. It looks like it's checking all commits instead of the latest one?

[Michsior14]

I've rewritten the history so there is only one commit to avoid the whitespace check failing (hopefully).

[Sapd]

Additionally this model support a few Equalizer presets (also custom settings) that I can successfully change via following commands:

Feel free to create another PR for that