Fetch the list of permitted languages for a contest from the back-end instead of hard-coding it on front-end

[arc9693]

Reference:

Online-Judge/website/components/editor.tsx

Lines 23 to 28 in 8f25fef

	const dict = {
	c: "c_cpp",
	"c++": "c_cpp",
	python3: "python",
	java: "java",
	};

Online-Judge/website/components/codeViewer.tsx

Lines 19 to 24 in 8f25fef

	const dict = {
	c: "c_cpp",
	"c++": "c_cpp",
	python3: "python",
	java: "java",
	};