Move Discourse and Slack to top of README (#3578)

* Move Discourse and Slack to the top of the README.

* Small fix

Author: garth-wells

README.md

@@ -12,6 +12,12 @@ DOLFINx is the computational environment of
 Solving Environment in C++ and Python. DOLFINx is a new version of
 DOLFIN and is actively developed.
 
+For questions about using DOLFINx, visit the [FEniCS
+Discourse](https://fenicsproject.discourse.group/) page or use the
+[FEniCS Slack channel](https://fenicsproject.slack.com/) (use
+[this](https://join.slack.com/t/fenicsproject/shared_invite/zt-1lraknsp1-6_3Js5kueDIyWgF192d3nA)
+link to sign up to the Slack channel).
+
 ## Documentation
 
 Documentation can be viewed at <https://docs.fenicsproject.org>.
@@ -191,19 +197,3 @@ Lesser General Public License for more details.
 You should have received a copy of the GNU Lesser General Public
 License along with DOLFINx. If not, see
 <https://www.gnu.org/licenses/>.
-
-## Contact
-
-For questions about using DOLFINx, visit the FEniCS Discourse page:
-
-<https://fenicsproject.discourse.group/>
-
-or use the FEniCS Slack channel:
-
-<https://fenicsproject.slack.com/>
-
-(use <https://join.slack.com/t/fenicsproject/shared_invite/zt-1lraknsp1-6_3Js5kueDIyWgF192d3nA> to sign up)
-
-For bug reports visit:
-
-<https://github.com/FEniCS/dolfinx>