i18n: Load script translations

[yuliyan]

Changes proposed in this Pull Request:

• Load translations for wc-calypso-bridge script.
• Build JSON translations files with wp i18n make-json [path-to-po-file].
• Exclude the /src path when generating the POT file to reduce the number of JSON translation files generated with make-json, as it uses the files paths references in the POT file to create the JSON files. A JSON translation files is loaded when its corresponding JS is enqueued in WordPress and given that the source modules never enqueued directly, generating translation files for those is unnecessary.
• Add filters for gettext calls with woocommerce to attempt to translate the same string using wc-calypso-bridge when there's no translation in the woocommerce domain. This change is targeted at gettext call used in this package with woocommerce text domain (such as #1, #2, #3, etc.).
• Load translation data for lazy loaded modules.

Related to 799-gh-Automattic/i18n-issues

• [ ] This PR is a very minor change/addition and does not require testing instructions (if checked you can ignore/remove the next section).

How to test the changes in this Pull Request:

• [ ] Have you followed the Writing high-quality testing instructions guide?

1. Checkout the branch locally.
2. Generate JSON translation files for one of the languages with wp i18n make-json languages/[language].po.
3. Sync the changes to your test site by following the instructions from pdDOJh-3ob-p2.
4. Open your test site and make sure set to the language you've generated the translation files for.
5. Navigate to /wp-admin/admin.php?page=wc-admin and confirm wc-calypso-bridge-js-translations translation data is loaded, i.e. the script <script id="wc-calypso-bridge-js-translations"> that loads the data using wp.i18n.setLocaleData() is printed on the page.
6. Navigate to /wp-admin/admin.php?page=wc-admin&path=%2Fmarketing and confirm translations for lazy loaded module Marketing are loaded as expected. The isEcommercePlan, isEcommercePlanTrial, isWooNavigationEnabled params on your test site must be true (can be overridden in class-wc-calypso-bridge-shared.php)

Other information:

• [ ] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests for your changes, as applicable?

FOR PR REVIEWER ONLY:

• [ ] I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.

[github-actions[bot]]

Size Change: +2.8 kB (+1.42%)

Total Size: 200 kB

Filename	Size	Change
./build/index.js	125 kB	+2.8 kB (+2.29%)

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `./build/53.js` | 1.05 kB | | `./build/index.css` | 883 B | | `./build/marketing.js` | 58 kB | | `./build/payment-gateway-suggestions.css` | 1.25 kB | | `./build/payment-gateway-suggestions.js` | 6.46 kB | | `./build/plugins.js` | 3.92 kB | | `./build/style-index.css` | 2.15 kB | | `./build/style-marketing.css` | 805 B |

_{compressed-size-action}

[yuliyan]

Thank your for reviewing the changes, @ilyasfoo!

I'm sorry I didn't make the instructions more clear, but rendering the translated strings is a separate problem caused by using incorrect text domain (i.e. woocommerce instead of wc-calypso-bridge).

The goal of this PR is to load the translation data into the i18n instance, i.e. to make sure wc-calypso-bridge-js-translations script is printed on the page.

I plan to follow up with creating a separate PR to update the text domain and another PR to commit translations files (i.e. run npm run prepare).

[yuliyan]

@ilyasfoo,

I've previously mentioned that some gettext calls were using incorrect text , but after further looking into it, I've noticed that some of the strings also exist in WooCommerce and updating the text domain would it from re-using the WooCommerce translations.

Instead, I took a different approach and add fallback translation lookup for gettext calls with woocommerce text domain that are missing tranaslations - https://github.com/Automattic/wc-calypso-bridge/pull/1472/commits/f1bceadbd63ad7006885325029e469a92f8c02bd. If you repeat your testing steps, you should now see the translated items.

I've also noticed that there were some lazy loaded modules that have their own translation files, that were previously not handled, so I've updated the PR to also handle this case in https://github.com/Automattic/wc-calypso-bridge/pull/1472/commits/9f81bc2882b65eaecebf8922bb6c1153c53e73ec.