fix(Fix FF bold font): fixed headline to have the same weight on firefox as it has in Chrome

packages/hindawi-theme/src/elements/Heading.js

@@ -6,18 +6,22 @@ export default {
   H1: css`
     color: ${th('heading.h1Color')};
     ${marginHelper};
+    font-weight: normal;
   `,
   H2: css`
     color: ${th('heading.h2Color')};
     ${marginHelper};
+    font-weight: normal;
   `,
   H3: css`
     color: ${th('heading.h3Color')};
     ${marginHelper};
+    font-weight: normal;
   `,
   H4: css`
     color: ${th('heading.h4Color')};
     ${marginHelper};
     ${displayHelper};
+    font-weight: normal;
   `,
 }