Add instagram_simple shortcode

Fixes #4748

config/services/servicesConfig.go

@@ -29,6 +29,7 @@ const (
 type Config struct {
 	Disqus          Disqus
 	GoogleAnalytics GoogleAnalytics
+	Instagram       Instagram
 }
 
 // Disqus holds the functional configuration settings related to the Disqus template.
@@ -43,6 +44,14 @@ type GoogleAnalytics struct {
 	ID string
 }
 
+// Instagram holds the functional configuration settings related to the Instagram shortcodes.
+type Instagram struct {
+	// The Simple variant of the Instagram is decorated with Bootstrap 4 card classes.
+	// This means that if you use Bootstrap 4 or want to provide your own CSS, you want
+	// to disable the inline CSS provided by Hugo.
+	DisableInlineCSS bool
+}
+
 func DecodeConfig(cfg config.Provider) (c Config, err error) {
 	m := cfg.GetStringMap(servicesConfigKey)
 

config/services/servicesConfig_test.go

@@ -33,6 +33,8 @@ someOtherValue = "foo"
 shortname = "DS"
 [services.googleAnalytics]
 id = "ga_id"
+[services.instagram]
+disableInlineCSS = true
 `
 	cfg, err := config.FromConfigString(tomlConfig, "toml")
 	assert.NoError(err)
@@ -44,6 +46,7 @@ id = "ga_id"
 	assert.Equal("DS", config.Disqus.Shortname)
 	assert.Equal("ga_id", config.GoogleAnalytics.ID)
 
+	assert.True(config.Instagram.DisableInlineCSS)
 }
 
 // Support old root-level GA settings etc.