epub converter: add style_config

doc/style_config

@@ -0,0 +1,70 @@
+config.allowedContent = {
+        sup: {
+            attributes: ['*'],
+            classes: ['*']
+        },
+        table: {
+            attributes: ['*'],
+            styles: ['*']
+        },
+        tr: {
+            attributes: ['*'],
+            styles: ['*']
+        },
+        th: {
+            attributes: ['*'],
+            classes: ['p-indent'],
+            styles: ['*']
+        },
+        td: {
+            attributes: ['*'],
+            classes: ['p-indent'],
+            styles: ['*']
+        },
+        tbody: {
+            attributes: ['*'],
+            styles: ['*']
+        },
+        thead: {
+            attributes: ['*'],
+            styles: ['*']
+        },
+        caption : {},
+        img : {
+            attributes: ['*'],
+            classes: ['*'],
+            styles: ['*']
+        },
+        p : {
+            styles: ['text-align', 'text-indent'],
+            classes: ['*']
+        },
+        strong : {},
+        i : {},
+        s : {},
+        u : {},
+        ul : {},
+        ol : {},
+        li : {
+            styles: ['text-align']
+        },
+        blockquote : {},
+        span : {
+            attributes: ['*'],
+            classes: ['*'],
+            styles: ['*']
+        },
+        a : {
+            attributes: ['href', 'data-anchor-id', 'data-chapter-id', 'placeholder'],
+            classes: ['link-to-anchor'],
+        },
+        iframe : {
+            attributes: ['*'],
+            classes: ['*'],
+            styles: ['*']
+        },
+        div : {
+            attributes: ['*'],
+            classes: ['youtube-embed-wrapper'],
+            styles: ['*']
+        }    };