feat: add markdown support to deno fmt (#8887)

This commit adds support for formatting markdown files with "deno fmt".

Additionally "--ext={js|jsx|ts|tsx|md}" flag was added to "deno fmt"
that allows to specify file type when providing contents over stdio.

1 files changed, 23 insertions, 0 deletions

diff --git a/cli/tests/badly_formatted_fixed.md b/cli/tests/badly_formatted_fixed.md
new file mode 100644
index 000000000..359a8aead
--- /dev/null
+++ b/cli/tests/badly_formatted_fixed.md
@@ -0,0 +1,23 @@
+# Hello Markdown
+
+```js
+console.log("Hello World");
+```
+
+```javascript
+console.log("Hello World2");
+```
+
+```ts
+function hello(name: string) {
+  console.log(name);
+}
+
+hello("alice");
+```
+
+```typescript
+function foo(): number {
+  return 2;
+}
+```