feat: add horizontal FOV converter

[wertiop121]

Closes momentum-mod/game/issues/2126

Adds a text box to change the horizontal FOV, which gets automatically converted to/from FOV.

Checks

• I have thoroughly tested all of the code I have modified/added/removed to ensure something else did not break
• I have followed semantic commit messages e.g. feat: Add foo, chore: Update bar, etc...
• My branch has a clear history of changes that can be easy to follow when being reviewed commit-by-commit
• My branch is functionally complete; the only changes to be done will be those potentially requested in code review
• All changes requested in review have been fixuped into my original commits.
• Fully tokenized all my strings (no hardcoded English strings!!) and supplied bulk JSON strings below

POEditor JSON Strings (if needed)

[
	{
		"term": "Settings_Video_Horizontal_FOV",
		"definition": "Import Horizontal FOV"
	},
	{
		"term": "Settings_Video_Horizontal_FOV_Info",
		"definition": "Import horizontal FOV from Quake 3.\n\nHorizontal FOV is an accurate measure of field-of-view, which is dependent on aspect ratio. Source's FOV is always 4:3-based (equivalent to horizontal FOV in a 4:3 aspect ratio), and on higher aspect ratios the view is stretched to fill the whole screen."
	}
        
]

[PeenScreeker]

Overall, looks good to me. Let a couple comments for minor changes I'd like to see. Nice work!

[tsa96]

Okay I've imported into POEditor but I'd like to add that link to the source of the FOV back, see convo above.

Also @wertiop121 in the future please just amend/fixup changes into your original commit. I can squash this PR into one commit but for PRs that contain more than one meaningful commit, we'd need you to fixup properly. Please ask us if you need a hand with Git, we're happy to explain stuff.