Placeholder links in Introduction and Explanation sections and other todos

[nibble0101]

Currently, links that point to other sections within the documentation have placeholder links to make the CI pass. It is only possible to add the correct links if the sections the links are pointing to have been merged. This issue is to keep track of the different sections in the Introduction and Explanation sections that have placeholder links which should be replaced.

Placeholder links

Introduction Section

Sub section	PR	Status
Overview of Wechaty documentation	#870	Partially fixed by this commit. Need to merge Advanced tutorials and other sections of Introduction for it to be completed
What is Wechaty	#871	Not started
What can you do with Wechaty	#873	No placeholder links. Everything is fine
Who are the users of Wechaty	#900	Not started
Getting started with Wechaty	#899	Not started
Main concepts in Wechaty	#904	Not started

Explanation Section

Sub section	PR	Status
Overview of the explanations section	#915	Not started
Wechaty chatbot development life cycle	#918	Not started
Software Development Kit	#930	No placeholder links. Everything is fine
Wechaty chatbot testing	#936	Not started
Wechaty DevOps tools	#949	Not started
Troubleshooting in Wechaty	#950	Replaced all placeholder links with actual links. Everything is fine
Wechaty chatbots architecture	#977	Not started

Other todos

Todo	PR	Status
Add Chatbot life cycle diagram	#918	Completed
Add more issues under troubleshooting section	#950	Completed
Split issues under troubleshooting section into categories	#950	Completed
Move community section out of Introduction section	#900	Waiting for mentor feedback on the suggestion

[lijiarui]

#900 Waiting for mentor feedback on the suggestion

I think this PR status should change to something like this: 'Mentor change request, will do later' ：）