Add style for classDiagram to dark/default theme

Copy classDiagram.less in forest theme to dark and default theme.

Issue: #454

src/less/dark/classDiagram.less

@@ -0,0 +1,69 @@
+g.classGroup text {
+  fill:@nodeBorder;
+  stroke:none;
+  font-family: 'trebuchet ms', verdana, arial;
+  font-size: 14px;
+}
+
+g.classGroup rect {
+  fill:@nodeBkg;
+  stroke: @nodeBorder;
+}
+
+g.classGroup line {
+  stroke: @nodeBorder;
+  stroke-width:1;
+}
+
+svg .classLabel .box {
+  stroke: none;
+  stroke-width:0;
+  fill: @nodeBkg;
+  opacity: 0.5;
+}
+
+svg .classLabel .label {
+  fill: @nodeBorder;
+}
+
+.relation {
+  stroke: @nodeBorder;
+  stroke-width: 1;
+  fill:none;
+}
+
+.composition{
+  fill : @nodeBorder;
+  stroke: @nodeBorder;
+  stroke-width:1;
+}
+#compositionStart {
+  .composition;
+}
+#compositionEnd {
+  .composition;
+}
+.aggregation{
+  fill : @nodeBkg;
+  stroke: @nodeBorder;
+  stroke-width:1;
+}
+#aggregationStart {
+  .aggregation;
+}
+#aggregationEnd {
+  .aggregation;
+}
+
+#dependencyStart {
+  .composition;
+}
+#dependencyEnd {
+  .composition;
+}
+#extensionStart {
+  .composition;
+}
+#extensionEnd {
+  .composition;
+}

src/less/dark/mermaid.less

@@ -2,7 +2,7 @@
 @import "flow";
 @import "sequenceDiagram";
 @import "gantt";
-@import "variables";
+@import "classDiagram";
 
 .node text {
   font-family: 'trebuchet ms', verdana, arial;

src/less/default/classDiagram.less

@@ -0,0 +1,69 @@
+g.classGroup text {
+  fill:@nodeBorder;
+  stroke:none;
+  font-family: 'trebuchet ms', verdana, arial;
+  font-size: 14px;
+}
+
+g.classGroup rect {
+  fill:@nodeBkg;
+  stroke: @nodeBorder;
+}
+
+g.classGroup line {
+  stroke: @nodeBorder;
+  stroke-width:1;
+}
+
+svg .classLabel .box {
+  stroke: none;
+  stroke-width:0;
+  fill: @nodeBkg;
+  opacity: 0.5;
+}
+
+svg .classLabel .label {
+  fill: @nodeBorder;
+}
+
+.relation {
+  stroke: @nodeBorder;
+  stroke-width: 1;
+  fill:none;
+}
+
+.composition{
+  fill : @nodeBorder;
+  stroke: @nodeBorder;
+  stroke-width:1;
+}
+#compositionStart {
+  .composition;
+}
+#compositionEnd {
+  .composition;
+}
+.aggregation{
+  fill : @nodeBkg;
+  stroke: @nodeBorder;
+  stroke-width:1;
+}
+#aggregationStart {
+  .aggregation;
+}
+#aggregationEnd {
+  .aggregation;
+}
+
+#dependencyStart {
+  .composition;
+}
+#dependencyEnd {
+  .composition;
+}
+#extensionStart {
+  .composition;
+}
+#extensionEnd {
+  .composition;
+}

src/less/default/mermaid.less

@@ -2,7 +2,7 @@
 @import "flow";
 @import "sequenceDiagram";
 @import "gantt";
-@import "variables";
+@import "classDiagram";
 
 .node text {
   font-family: 'trebuchet ms', verdana, arial;