docs: add examples for Near host functions

packages/near-sdk-js/src/api.ts

@@ -293,6 +293,15 @@ export function storageReadRaw(key: Uint8Array): Uint8Array | null {
  * Reads the utf-8 string value from NEAR storage that is stored under the provided key.
  *
  * @param key - The utf-8 string key to read from storage.
+ * 
+ * @example
+ * ```ts
+ * import { near } from "near-sdk-js";
+ * 
+ * near.storageRead("key"); // -> null
+ * near.storageWrite("key", "value");
+ * near.storageRead("key"); // -> "value"
+ * ```
  */
 export function storageRead(key: string): string | null {
   const ret = storageReadRaw(encode(key));
@@ -315,6 +324,15 @@ export function storageHasKeyRaw(key: Uint8Array): boolean {
  * Checks for the existence of a value under the provided utf-8 string key in NEAR storage.
  *
  * @param key - The utf-8 string key to check for in storage.
+ * 
+ * @example
+ * ```ts
+ * import { near } from "near-sdk-js";
+ * 
+ * near.storageHasKey("key"); // -> false
+ * near.storageWrite("key", "value");
+ * near.storageHasKey("key"); // -> true
+ * ```
  */
 export function storageHasKey(key: string): boolean {
   return storageHasKeyRaw(encode(key));
@@ -356,6 +374,15 @@ export function storageWriteRaw(key: Uint8Array, value: Uint8Array): boolean {
  *
  * @param key - The utf-8 string key under which to store the value.
  * @param value - The utf-8 string value to store.
+ * 
+ * @example
+ * ```ts
+ * import { near } from "near-sdk-js";
+ * 
+ * near.storageRead("key"); // -> null
+ * near.storageWrite("key", "value");
+ * near.storageRead("key"); // -> "value"
+ * ```
  */
 export function storageWrite(key: string, value: string): boolean {
   return storageWriteRaw(encode(key), encode(value));
@@ -374,6 +401,17 @@ export function storageRemoveRaw(key: Uint8Array): boolean {
  * Removes the value of the provided utf-8 string key from NEAR storage.
  *
  * @param key - The utf-8 string key to be removed.
+ * 
+ * @returns Removes the value stored under the given key. If key-value existed returns true, otherwise false.
+ * 
+ * @example
+ * ```ts
+ * import { near } from "near-sdk-js";
+ * 
+ * near.storageRemove("key"); // -> false
+ * near.storageWrite("key", "value");
+ * near.storageRemove("key"); // -> true
+ * ```
  */
 export function storageRemove(key: string): boolean {
   return storageRemoveRaw(encode(key));