Markdown link strategy

Add the following instructions in the documentation.

## To verify if links between documentation pages are working
- Install Visual Studio Extension: [`Markdown link checker`](https://marketplace.visualstudio.com/items?itemName=dlyz.md-link-checker).
Unlike the Visual Studio Code default md link checker, this link checker extension is able to verify **_relative file links_** (i.e. using relative path from the open md file, pointing to a specific filepath. When linking to a page, its file extension e.g. `.md` must be included in the link).
- CTRL+Shift+P, type `markdown link checker recheck...` and press enter:

- Squiggly red line will appear below any broken link. This only works for **_relative file links_** (i.e. using relative path from the open md file, pointing to a specific filepath. When linking to a page, its file extension e.g. `.md` must be included in the link).

## To link to another Markdown file in the Documentation
**General rule: make sure that all Markdown files do not have whitespaces in their filename! Use underscores or dashes instead.**
Otherwise the following won't work (in the URL link, you will need to replace whitespaces with `%20` symbols, or the link checker will not understand the link; in the documentation website the link will still work though).

In Visual Studio Code:
- Open the md file you want to edit.
- In the Explorer, find the file you want to link to.
- Holding Shift, click the file and drag-drop it into the open md file where you want to place a link.
- A link will be created. This link will be a **_relative file link_**, so the `Markdown link checker` extension will be able to verify if the file is findable.