emmet extension should use shared tsconfig

[mjbvz]

Replace the emmet extension 's custom tsconfig with one that extends our new shared tsconfig:

{
	"extends": "../shared.tsconfig.json",
	"compilerOptions": {
		"outDir": "./out"
	},
	"exclude": [
		"node_modules",
		".vscode-test"
	],
	"include": [
		"src/**/*"
	]
}

This shared tsconfig will ensure that all of our extensions target the same environment. It will also help enforce consistent code quality standards across extensions.

As part of adopting the shared tsconfig, code changes are needed in the emmet extension to make sure it can build in strict mode with noUnusedLocals and noUnusedParameters enabled. Please let me know if you have any questions about fixing these errors.