Minor changes to improve readability and fix typos

I've changed the link for contribution guidelines to an internal link within the guide (rather than an external link to GitHub that links back to the guide).

docs/basics/planning.md

@@ -36,17 +36,17 @@ Before starting work on a bug your first step should be to check  [JIRA](https:/
 
 In order to reproduce the bug you can reproduce the issue in the appropriate [CiviCRM Sandbox](https://civicrm.org/sandboxes). Enabling debugging can help to get more details.
 
-Make sure to check [the contribution guidelines](https://github.com/civicrm/civicrm-core/blob/master/.github/CONTRIBUTING.md) for more information on how to create your PR.
+Make sure to check [the contribution guidelines](/core/contributing.md) for more information on how to create a pull request.
 
 ## Recommendations
 
-**Open a free [GitHub](https://github.com/) account** for revision control. The official CiviCRM [repositories](https://github.com/civicrm) are housed in `git` repositories on GitHub.  If you use GitHub you will find it easy to access the latest source-code, to submit pull requests for any patches you create and to collaborate with many other CiviCRM developers who also use GitHub.
+**Open a free [GitHub](https://github.com/) account** for version control. The official CiviCRM [repositories](https://github.com/civicrm) are housed in `git` repositories on GitHub.  If you use GitHub you will find it easy to access the latest source-code, to submit pull requests for any patches you create and to collaborate with many other CiviCRM developers who also use GitHub.
 
-**Install the [buildkit](https://github.com/civicrm/civicrm-buildkit)**, ideally as a [vagrant virtual-machine](https://github.com/civicrm/civicrm-buildkit-vagrant) or using one of available `docker` images ([1](https://github.com/progressivetech/docker-civicrm-buildkit), [2](https://github.com/ErichBSchulz/dcbk)). The buildkit is not an absolute requirement but it is definitely the fastest path to a good development experience!
+**Install the [buildkit](https://github.com/civicrm/civicrm-buildkit)**, ideally as a [vagrant virtual-machine](https://github.com/civicrm/civicrm-buildkit-vagrant) or using one of available `docker` images ([progressivetech](https://github.com/progressivetech/docker-civicrm-buildkit) or [EricBSchulz](https://github.com/ErichBSchulz/dcbk)). The buildkit is not an absolute requirement but it is definitely the fastest path to a good development experience!
 
-**From the outset, [automate testing](/testing/setup.md)**. In the current climate of rapid evolution of not just CiviCRM, but also it's myriad of dependancies, automated testing of PHP code with `phpunit` and javascript with tools like `karma` and `jasmine` is essential. Start all your work by considering how you will provide automated testing for it. Starting with the buildkit will make this much simpler for you to set up. Getting started with unit-testing may seem daunting and onerous when you start, but you will soon come to love the freedom it gives you. If you are unsure how to proceed with testing ask the [community](/basics/community.md).
+**From the outset, [automate testing](/testing/setup.md)**. In the current climate of rapid evolution of not just CiviCRM, but also it's myriad of dependencies, automated testing of PHP code with `phpunit` and javascript with tools like `karma` and `jasmine` is essential. Start all your work by considering how you will provide automated testing for it. Starting with the buildkit will make this much simpler for you to set up. Getting started with unit-testing may seem daunting and onerous when you start, but you will soon come to love the freedom it gives you. If you are unsure how to proceed with testing ask the [community](/basics/community.md).
 
-**Create a native [extension](/extensions/index.md)**. If you have new functionality to add to CiviCRM, it probably belongs in an extension.  "Native" extensions will install into all CiviCRM sites regardless of the  underlying CMS used (Drupal or WordPress), making it easy to share your extension with the CiviCRM community.
+**Create a native [extension](/extensions/index.md)**. If you have new functionality to add to CiviCRM, it probably belongs in an extension.  "Native" extensions will install into all CiviCRM sites regardless of the  underlying CMS used (Drupal, WordPress, Joomla or Backdrop), making it easy to share your extension with the CiviCRM community.
 
 **Use the [API](/api/index.md) and [hooks](/hooks/index.md)** to access and manage CiviCRM data in any patch, native extension, CMS module, or external program that you develop. The API will function as expected with every new release and backwards compatibility of the API is maintained for several versions of CiviCRM.