font-patcher: Vertically centered glyphs not really centered ('valign' = 'c')

🗹 Requirements

[X] A brief but descriptive title of your issue
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🎯 Vertical alignment slightly off with some fonts

A lot (most) of the glyphs added are vertically centered ('valign' = 'c' in font-patcher). With some source fonts the alignment is not very good and for example (because of its symmetry it makes the behavior most notable) the Ubuntu logo  (0xF31B) is above or below the 'perceived' middle. The middle is usually perceived as the vertical center of the square brackets [, the height of the minus -, the intersection of the lines of capital X, or the left tip of less then <

The issue has already been researched and a pull request has been prepared (link to PR coming here).

🔧 Your Setup

These fonts are affected (amount of shift):
- Overpass 9%
- Monofu 12%
- Hermit 4%
- Agave 7%
- Inconsolata 6%
- CascadiaCode 7%
Which terminal emulator are you using (e.g. iterm2, urxvt, gnome, konsole)? Gnome terminal, tilix, fontforge
Are you using OS X, Linux or Windows? And which specific version or distribution? Ubuntu 20.10

★ Optional

As example the screenshot with Gnome terminal and CaskaydiaCove Nerd Font Mono Regular 42:

Ubuntu (0xF31B) too high
Powerline Triangular Stuff too high (externds into line above)

(All vertically centered new glyphs are too high, e.g. 'git branch' 0xE0A0, 'rain at night' 0xF024.)

Expected would be:

More images of all the fonts will be shown in the MR.

ryanoasis / nerd-fonts