docs(plugin-flow-builder): update github url in REDME and update docs (…

…#2607)

<!-- _Set as [Draft
PR](https://github.blog/2019-02-14-introducing-draft-pull-requests/) if
it's not ready to be merged_.

[PR best practices
Reference](https://blog.codeminer42.com/on-writing-a-great-pull-request-37c60ce6f31d/)
-->

## Description
Update the botonic documentation. The flow builder plugin is only
published in the master-lts branch.
<!--
- Must be clear and concise (2-3 lines).
- Don't make reviewers think. The description should explain what has
been implemented or what it's used for. If a pull request is not
descriptive, people will be lazy or not willing to spend much time on
it.
- Be explicit with the names (don't abbreviate and don't use acronyms
that can lead to misleading understanding).
- If you consider it appropriate, include the steps to try the new
features.
-->

docs/docs/plugins/plugin-flow-builder.md

@@ -13,7 +13,7 @@ For more information, refer to **[GitHub](https://github.com/hubtype/botonic/tre
 
 ## What Does This Plugin Do?
 
-Botonic Plugin Flow Builder is one of the **[available](https://github.com/hubtype/botonic/tree/master/packages)** plugins for Botonic.
+Botonic Plugin Flow Builder is one of the **[available](https://github.com/hubtype/botonic/tree/master-lts/packages)** plugins for Botonic.
 
 Flow Builder is a no-code, drag-and-drop chatbot builder that makes the process of creating and editing chatbot journeys faster and more intuitive.
 From [Hubtype](https://www.hubtype.com/) we offer a suite of tools and features that let you build, test and deploy both automated and agent-based journeys at scale. This plugin allows you to connect to our Flow Builder.