[FIX] compiler: correctly escape special characters in template literals

Previously, there were a few places where the compiler would create
strings from template content and emit them as template literals, but
didn't properly escape characters or character sequences with special
meanings, in particular: backslashes, backticks, and interpolation
sigils.

This commit fixes this in:
- block creation (interpolation sigils were not escaped)
- text node creation (no escaping was performed)
- comment not creation (no escaping was performed)
- default values for t-esc (no escaping was performed)
- body of a t-set (no escaping was performed)

tests/compiler/comments.test.ts

@@ -26,4 +26,19 @@ describe("comments", () => {
         </div>`;
     expect(renderToString(template)).toBe("<div><span>true</span></div>");
   });
+
+  test("comment node with backslash at top level", () => {
+    const template = "<!-- \\ -->";
+    expect(renderToString(template)).toBe("<!-- \\ -->");
+  });
+
+  test("comment node with backtick at top-level", () => {
+    const template = "<!-- ` -->";
+    expect(renderToString(template)).toBe("<!-- ` -->");
+  });
+
+  test("comment node with interpolation sigil at top level", () => {
+    const template = "<!-- ${very cool} -->";
+    expect(renderToString(template)).toBe("<!-- ${very cool} -->");
+  });
 });