Add option for internal links

Thanks for your contribution! I'll provide a review soon but it looks like it's working nicely at first glance.

1. +++ b/config/install/page_load_progress.settings.yml
   @@ -3,3 +3,4 @@ page_load_progress_elements: '.page-load-progress-submit'
    page_load_progress_esc_key: true
   

   Please put this before page_load_progress_esc_key. Explanation below.

2. +++ b/js/page_load_progress.js
   @@ -28,6 +29,29 @@
   +      // Add the lock behavior for internal links opened in the same tab that are not in a modal.
   

   Please wrap the comment at 80 cols.

3. +++ b/js/page_load_progress.js
   @@ -28,6 +29,29 @@
   +          // Return if the link is external.
   ...
   +          // Return if the user is attempting to open in a new tab.
   +          // Source: https://stackoverflow.com/a/20087506/9637665.
   

   'Return' is for programmers, but if we have a comment it's also for non-programmers to understand what the code is doing IMO. Instead, what about saying "Do not lock the screen if the user is attempting to open in a new tab."?

4. +++ b/js/page_load_progress.js
   @@ -28,6 +29,29 @@
   +          // Return if the link is external.
   

   Same here: "Do not lock the screen if the link is within a modal".

5. +++ b/js/page_load_progress.js
   @@ -28,6 +29,29 @@
   +          // Return if the user is attempting to open in a new tab.
   

   Same here: "Do not lock the screen if the user is attempting to open in a new tab.".

6. +++ b/js/page_load_progress.js
   @@ -28,6 +29,29 @@
   +          // Source: https://stackoverflow.com/a/20087506/9637665.
   

   Thanks for adding the source, very helpful!

7. +++ b/page_load_progress.module
   @@ -71,6 +71,7 @@ function page_load_progress_page_attachments(array &$attachments) {
          'esc_key' => $config->get('page_load_progress_esc_key'),
   

   Please put this before 'esc_key'. Explanation below.

8. +++ b/src/Form/SettingsForm.php
   @@ -76,6 +76,13 @@ class SettingsForm extends ConfigFormBase {
   +    $form['page_load_progress_internal_links'] = [
   

   I think this checkbox should live within the VISIBILITY CONDITIONS fieldset because it's also one. Use $form['visibility_conditions']['page_load_progress_internal_links']

9. +++ b/src/Form/SettingsForm.php
   @@ -76,6 +76,13 @@ class SettingsForm extends ConfigFormBase {
   +      '#description' => $this->t('On some sites you may want internal links to use the image lock for internal links. The lock does not trigger on links opened from a modal or when the user is trying to open the link in a new tab.'),
   

   The #title already takes care of explaining what this checkbox is for so I think we could drop 'On some sites you may want internal links to use the image lock for internal links.' entirely.

10. +++ b/src/Form/SettingsForm.php
    @@ -88,6 +95,7 @@ class SettingsForm extends ConfigFormBase {
           ->set('page_load_progress_esc_key', $form_state->getValue('page_load_progress_esc_key'))
    +      ->set('page_load_progress_internal_links', $form_state->getValue('page_load_progress_internal_links'))
    

    Please put this above 'page_load_progress_esc_key' as per the above remark.

For readability, please always keep all patches submitted in the issue queue so that it's easier to see changes. Also, creating an interdiff is best.

Here's the interdiff.

+++ b/js/page_load_progress.js
@@ -29,21 +29,21 @@
+          // Do not lock the screen if the user is attempting to open in a new tab.

This should be wrapped at 80 cols. Can be fixed on commit.

Otherwise it looks great, thank you. The only remaining bits I can think of ATM are:

• Tests (let me know if you need any help with it, should be pretty simple with the existing Boolean examples)
• Changes to page_load_progress.schema.yml to add the missing page_load_progress_internal_links

Let's run tests.

Added a few other nitpicks (like consistently naming the 'screen lock' a throbber).

This looks great to me. Committed, thanks!