feat: auto complete katex environment

src/renderer/plugins/editor-md-syntax.ts

@@ -58,6 +58,7 @@ class MdSyntaxCompletionProvider implements Monaco.languages.CompletionItemProvi
     { name: '/ + MindMap', insertText: '+ ${1:Subject}{.mindmap}\n    + ${2:Topic}' },
     { name: '/ $ Inline KaTeX', insertText: '$$1$' },
     { name: '/ $$ Block KaTeX', insertText: '$$$1$$\n' },
+    { name: '/ \\begin KaTeX Environment', insertText: '\\begin{$1}\n\\end{$1}' },
     { name: '/ ``` ECharts', insertText: '```js\n// --echarts-- \nchart => chart.setOption({\n  xAxis: {\n    type: "category",\n    data: ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]\n  },\n  yAxis: {\n    type: "value"\n  },\n  series: [\n    {\n      data: [150, 230, 224, 218, 135, 147, 260],\n      type: "line"\n    }\n  ]\n}, true)\n```\n' },
     { name: '/ ``` Run Code', insertText: '```js\n// --run--\n${1:await new Promise(r => setTimeout(r, 500))\nctx.ui.useToast().show("info", "HELLOWORLD!")\nconsole.log("hello world!")}\n```\n' },
     { name: '/ ``` Applet', insertText: '```html\n<!-- --applet-- ${1:DEMO} -->\n<button onclick="ctx.ui.useToast().show(`info`, `HELLOWORLD!`)">TEST</button>\n```\n' },