RFR: Update Readme with macOs specifics [v2]

[Brice Dutheil]

On Tue, 29 Mar 2022 10:41:50 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> README.md line 15:
>> 
>>> 13: ```
>>> 14: 
>>> 15: <details><summary>Using a local installation of LLVM</summary>
>> 
>> Can we do this in bold, and also perhaps use the quote mechanism - e.g.
>> 
>>> <details><summary><b>Using a local installation of LLVM</b></summary>Some text</summary>
>
>> Can we do this in bold, and also perhaps use the quote mechanism - e.g.
>> 
>> > Using a local installation of LLVMSome text
> 
> The above was done like this:
> 
> 
>> <details><summary><b>Using a local installation of LLVM</b></summary>Some text</summary>

Done

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PR: https://git.openjdk.java.net/jextract/pull/10