unify markdown editor style

simplemde-dark.css

@@ -434,7 +434,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
   border-bottom-right-radius: 3px;
   color: #aaa;
   font-family: inherit;
-  font-size: 18px;
   height: auto;
   line-height: 1.5;
   min-height: 300px;
@@ -540,30 +539,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
   line-height: 2;
 }
 
-.cm-s-paper.CodeMirror .CodeMirror-code .cm-header-1 {
-  font-size: 32px;
-}
-
-.cm-s-paper.CodeMirror .CodeMirror-code .cm-header-2 {
-  font-size: 26px;
-}
-
-.cm-s-paper.CodeMirror .CodeMirror-code .cm-header-3 {
-  font-size: 24px;
-}
-
-.cm-s-paper.CodeMirror .CodeMirror-code .cm-header-4 {
-  font-size: 22px;
-}
-
-.cm-s-paper.CodeMirror .CodeMirror-code .cm-header-5 {
-  font-size: 20px;
-}
-
-.cm-s-paper.CodeMirror .CodeMirror-code .cm-header-6 {
-  font-size: 18px;
-}
-
 .cm-s-paper.CodeMirror .CodeMirror-code .cm-header,
 .cm-s-paper.CodeMirror .CodeMirror-code .cm-strong {
   font-weight: 600;
@@ -573,7 +548,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
   background-color: rgba(255, 255, 255, 0.05);
   font-family: Menlo, Monaco, Consolas, "Liberation Mono", "Courier New",
     monospace;
-  font-size: 14px;
   padding: 6px 0 4px;
 }
 
@@ -619,7 +593,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
   color: #aaa;
   display: none;
   font-family: inherit;
-  font-size: 18px;
   line-height: 1.5;
   overflow: auto;
   padding: 0 14px 14px;
@@ -629,7 +602,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
   background-color: rgba(255, 255, 255, 0.05);
   font-family: Menlo, Monaco, Consolas, "Liberation Mono", "Courier New",
     monospace;
-  font-size: 14px;
   line-height: 1.2;
   margin-top: 14px;
   overflow: auto;
@@ -639,7 +611,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
 .cm-s-paper .editor-preview pre code,
 .cm-s-paper .editor-preview-side pre code {
   background-color: transparent;
-  font-size: 14px;
   padding: 0;
 }
 
@@ -703,7 +674,6 @@ div.cm-s-paper.CodeMirror span.CodeMirror-nonmatchingbracket {
   border-bottom: 0;
   border-top-left-radius: 3px;
   border-top-right-radius: 3px;
-  font-size: 18px;
   padding: 0 14px;
   position: relative;
   -webkit-user-select: none;