doc(es): Improve documentation (#10247)

**Description:**

Add some documentations to some methods.

**Related issue:**

 - Closes #10244

Author: kdy1

.changeset/kind-kangaroos-return.md

@@ -0,0 +1,7 @@
+---
+swc_common: patch
+swc_ecma_ast: patch
+swc_core: patch
+---
+
+doc(es): Improve documentation

crates/swc_common/src/syntax_pos.rs

@@ -136,6 +136,16 @@ better_scoped_tls::scoped_tls!(
     ///
     /// # Usages
     ///
+    /// ## Configuring
+    ///
+    /// ```rust
+    /// use swc_common::GLOBALS;
+    ///
+    /// GLOBALS.set(&Default::default(), || {
+    ///     // Do operations that require span hygiene
+    /// });
+    /// ```
+    ///
     /// ## Span hygiene
     ///
     /// [Mark]s are stored in this variable.

crates/swc_ecma_ast/src/ident.rs

@@ -572,6 +572,14 @@ impl Ident {
         }
     }
 
+    /// Creates a new private identifier. A private identifier is an identifier
+    /// that is guaranteed to be unique.
+    ///
+    /// See https://swc.rs/docs/contributing/es-commons/variable-management for more details.
+    ///
+    /// Note: This method requires configuring
+    /// [GLOBALS](`swc_common::GLOBALS`) because this method use [`Mark::new`]
+    /// internally.
     #[inline(never)]
     pub fn new_private(sym: Atom, span: Span) -> Self {
         Self::new(sym, span, SyntaxContext::empty().apply_mark(Mark::new()))