add strikethrough highlight

client/components/codeEditor/codeEditor.less

@@ -100,6 +100,10 @@
 			vertical-align : sub;
 			color          : rgb(123, 123, 15);
 		}
+		.cm-strikethrough {
+			text-decoration: line-through;
+		}
+
 		.cm-definitionList {
 			.cm-definitionTerm { color : rgb(96, 117, 143); }
 			.cm-definitionColon:not(:has(.cm-comment)) {

client/components/codeEditor/customHighlight.js

@@ -16,6 +16,7 @@ const customTags = {
 	definitionTerm  : 'definitionTerm', // .cm-definitionTerm
 	definitionDesc  : 'definitionDesc', // .cm-definitionDesc
 	definitionColon : 'definitionColon', // .cm-definitionColon
+	strikethrough   : 'strikethrough', // .cm-strikethrough
 
 	//CSS
 
@@ -81,6 +82,23 @@ export function tokenizeCustomMarkdown(text) {
 			}
 		}
 
+		// --- Strikethrough ---
+		if(/\~/.test(lineText)) {
+			const strikethroughRegex = /~(?!\s)(.+?)(?<!\s)~/g;
+
+			let match = strikethroughRegex.exec(lineText);
+			let type = customTags.strikethrough;
+
+			if(match) {
+				tokens.push({
+					line : lineNumber,
+					type,
+					from : match.index,
+					to   : match.index + match[0].length,
+				});
+			}
+		}
+
 		// --- single line def list ---
 		const singleLineRegex = /^(?=.*[^:])(.+?)(\s*)(::)([^\n]*)$/dmy;
 		const match = singleLineRegex.exec(lineText);