RFR: Update Readme with macOs specifics [v2]

[Maurizio Cimadamore]

On Tue, 29 Mar 2022 10:41:08 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Brice Dutheil has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix review comments
>
> 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>

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