Research section: Add content to Bitcoin Core App website

[mouxdesign]

Various UX research efforts have been done on Bitcoin Core App as well as on the node side.

Opening this issue with a draft of content for a research section on the Bitcoin Core app website. Sharing the draft doc here which has the following headings:

• Intro to research
• Research efforts summary
• How research is organised
• Past research efforts
• How to contribute

Please feel free to have a read through at the moment, just checking in if the structure provides enough context for someone who knows little about research and if the headings are suitable.

[mouxdesign]

Continued to work on the write up:

• Added in one image showing a high level overview of the research efforts done
• Improved the copy for readability

[GBKS]

The research page was added in #94. Can we close this issue?