Rails 6 Herokuデプロイ時のエラー(Precompiling assets failed.)

Herokuデプロイ中に起きたエラー

methods since the "loose" mode option was set to "true" for @babel/plugin-proposal-class-properties.
       The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
        ["@babel/plugin-proposal-private-methods", { "loose": true }]
       to the "plugins" section of your Babel config.
       Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "true" for @babel/plugin-proposal-class-properties.
       The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
        ["@babel/plugin-proposal-private-methods", { "loose": true }]
       to the "plugins" section of your Babel config.
       Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "true" for @babel/plugin-proposal-class-properties.
       The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
        ["@babel/plugin-proposal-private-methods", { "loose": true }]
       to the "plugins" section of your Babel config.

 !
 !     Precompiling assets failed.
 !
 !     Push rejected, failed to compile Ruby app.
 !     Push failed

[Precompiling assets failed.]

参考記事

Rails6系を使用している時に、
herokuへのアプリケーションデプロイでPrecompile assets failedになることがあるっぽい
よくみてみると使用している
Bootstrapのバージョンが5系の時は

$ yarn add popperjs/core

を実行してから
再度デプロイをすることで、問題なくcompileができるようになるっぽい。

ちなみに使用しているBootstrapが4系の時は

$ yarn add popper.js

を実行すれば問題ないかも。