Apply markdown formatting to the GitHub docs README

Tue Apr 18 13:05:10 UTC 2023

Sorry - that must have slipped through the cracks. Now merged.

Gavin

> On 10 Apr 2023, at 22:52, Tesla Zhang <ice1000kotlin at foxmail.com> wrote:
> 
> Hi Amber developers,
> 
> I have created a pull request on GitHub https://github.com/openjdk/amber-docs/pull/17 to apply markdown formatting for the readme file, and it's getting no attention for almost a year.
> 
> I wish that this can be merged :) if I am missing something in the PR, please let me know!
> 
> Best regards,
> Tesla