feat: java class/interface/record/enum/exception icons

[prazdevs]

closes #161

@sgoudham feel free to change/adapt class colors to what seems fitting, i used shades of blue as it was already blue. Also I didnt bind them to anything in VSC as it cannot differentiate the type of java file (besides extension)

[sgoudham]

Thanks so much for creating them, I think they look amazing!

(Ignore the Angular icon for Exception as I was just trying some things out)

A few comments from me:

1. Looks like Exception is also supported so it'd be good to have an icon for that. For reference, Atom's icon is a lightning bolt as shown below:

   

2. I'd also remove all the existing java_alt icons and maybe just have one singular red duke icon since it is a mascot.

3. I think it makes sense to prepend the icons with java- or equivalent to avoid conflicts with reserved keywords if people are auto-generating them. I know you said that it might be good to keep it vague but I think it's better to be specific since I think it's a bit unlikely that people will want to use Java class icons for Kotlin class icons. Happy to have my mind changed here though.

[sgoudham]

I've added an exception icon, removed the java_alt icons and renamed the icons to be prefixed with java-.
Going to leave it for a bit before merging in case you really disagree with some of my changes @prazdevs

[sgoudham]

Updated preview: