Fix coverage failure

    CompilerError: Stack too deep when compiling inline assembly: Variable headStart is 1 slot(s) too deep inside the stack.
    issue description: ethereum/solidity#10354
    workaround: sc-forks/solidity-coverage#636

Author: andy-at-mask

.solcover.js

@@ -0,0 +1,3 @@
+module.exports = {
+    configureYulOptimizer: true,
+};