Added How-to Guides section

[cardboardcode]

Purpose of Pull Request 🔖

This Pull Request (PR) is aimed at appending a new catch-all section called How-to Guides, addressing the suggestion brought in in #120.

Details are covered in the aforementioned issue thread.

Summary of Edits 📚

• Added new section under SUMMARY.md.
• Created a new .md document, howto_guides.md with a short introduction on what the section is all about.

Remarks 💬

To set a proper example of what is a good how-to guide, I will write up a article to be added under the new How-to Guides section within the coming weeks.

[xiyuoh]

General thoughts:

• Recommend to remove all the bold text, since the description is pretty short anyway so we probably don't have to emphasize on every other sentence
• It could be good to move Navigation Graph Strategies to this section, since it is pretty nested and could be difficult for users to locate. Also because it's more for users who already have basic knowledge of creating nav graphs.

Since ROS 2's Tutorials and How-to Guides differ in level of complexity/user knowledge, we can apply similar guidelines to Open-RMF to consider where to place future guides.

[cardboardcode]

@xiyuoh Thank you for the feedback so far.

Planning to move Navigation Graph Strategies into How-to Guides section as per feedback.

Will aim to do so before today's Open-RMF Community Meeting.

[cardboardcode]

@xiyuoh Moved the aforementioned Navigation Graph Strategies section under How-to Guides.

Ready for review again.

[cardboardcode]

@xiyuoh Friendly ping on this for merging.