Readme fixes. [skip ci]
Thank you for your interest in participating to the development!
A large fraction of Meson is contributed by people outside
-the core team and we are **excited** to see what you do.
+the core team and we are *excited* to see what you do.
**Contribution instructions can be found on the website**
- @ http://mesonbuild.com/Contributing.html
+ @ https://mesonbuild.com/Contributing.html
