feat: Add 'delete' into the view context menu

[xqzlgy2]

Enable User to delete package/file in context menu like below.

• All deleted file will be moved to Recycle Bin/Trash by default.
• Added File/Type into ContextValueType to distinguish common files and Java source files.
• Added +enum/+class/+interface as attributes to Type for detecting different kinds of source files.
• Added key binding for delete.
• Preserve focus when open file through Java project explorer

part of #207

[0dinD]

Awesome, this is just what I wanted! If it's not too much to ask for, do you think you could add a 'rename' option to the menu? I think you can do it via the extension API, and hopefully vscode-java would be able to pick up on that rename event, in order to provide a refactoring to change the class name. (Which it does when you rename a java file from the file explorer.) I understand if this is not trivial to add because of API limitations, but it would be very nice to have if it's possible to implement.

[jdneo]

@0dinD Yes, rename will be added after this PR.

// BTW, we will have the National Holiday at our side so it will happen after the holiday (about in Mid. Oct.)

[jdneo]

@xqzlgy2 Could you please also investigate if it is possible to set default keyboard shortcut for this command in package.json?

[jdneo]

Thanks @xqzlgy2!