[CD/CI] Fix gh pages deploy (#461)

### What
Fix gh pages [deploy](https://github.com/stellar/js-stellar-base/runs/3436212203?check_suite_focus=true):
1. The jsdoc command needs to be run by yarn with `yarn jsdoc`.
2. There was a wrong jsdoc return type in `asset.js`.

.github/workflows/gh_pages.yml

@@ -21,7 +21,7 @@ jobs:
         run: gulp
 
       - name: Generate JSDoc
-        run: jsdoc -c .jsdoc.json --verbose
+        run: yarn jsdoc -c .jsdoc.json --verbose
 
       - name: Deploy to GH Pages
         uses: JamesIves/github-pages-deploy-action@12a916dfb718ab8fc2ec3ad7cb731a89d7d23332

src/asset.js

@@ -192,7 +192,7 @@ export class Asset {
    * @static
    * @param {Asset} assetA - The first asset in the lexicographic order.
    * @param {Asset} assetB - The second asset in the lexicographic order.
-   * @return {-1 | 0 | 1} `-1` if assetA < assetB, `0` if assetA == assetB, `1` if assetA > assetB.
+   * @return {number} `-1` if assetA < assetB, `0` if assetA == assetB, `1` if assetA > assetB.
    * @memberof Asset
    */
   static compare(assetA, assetB) {