Additional "Cancel" and "VSCode" icon

[halirutan]

In addition to the new icons, I have removed the lcd antialiasing for icons. We discussed several times that this setting makes icons crispy on Linux while it doesn't seem to have a major effect on other operating systems.

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• Change in CHANGELOG.md described
• Tests created for changes
• Manually tested changed features in running JabRef
• Screenshots added in PR description (for bigger UI changes)
• Ensured that the git commit message is a good one
• Check documentation status (Issue created for outdated help page at help.jabref.org?)

[koppor]

I think, we could have reused the original material design font without copy and pasting and icon? Let's see, how I can include the new icon, because constructor of JabRefIcon needs a MaterialDesignIcon.

[tobiasdiez]

@koppor This is on the maintable-beta branch...there JabRefIcon is an interface.

[halirutan]

@koppor That was a design-flaw I fixed for the maintable branch. It basically only needs to implement the GlyphIcons interface. In essence it was a more or less simple refactoring and now the JabRefIcons constructor can take both our Icons and MD icons. Look at the org.jabref.gui.icon package on the maintable branch. Maybe you can cherry pick it somehow.