Fix some playground HTML errors and warnings
Fix some playground HTML errors and warnings

existentialism/prettier,azz/prettier,existentialism/prettier,rattrayalex/prettier,prettier/prettier,existentialism/prettier,existentialism/prettier,prettier/prettier,rattrayalex/prettier,prettier/prettier,azz/prettier,lydell/prettier,lydell/prettier,prettier/prettier,lydell/prettier,azz/prettier,rattrayalex/prettier,lydell/prettier,jlongster/prettier,azz/prettier