message: add a reminder to change README on flag change.
diff: #include "verilog/analysis/verilog_linter.h"
  #include "verilog/analysis/verilog_linter_configuration.h"
  +// LINT.IfChange
  +
  ABSL_FLAG(bool, check_syntax, true,
  "If true, check for lexical and syntax errors, otherwise ignore.");
  ABSL_FLAG(bool, parse_fatal, true,
  @@ -48,6 +50,8 @@ ABSL_FLAG(
  "Markdown and exit immediately. Intended for the output to be written "
  "to a snippet of Markdown.");
  +// LINT.ThenChange(README.md)
  +
  using verilog::LinterConfiguration;
  int main(int argc, char** argv) {
  