[llvm] [Offload] Expand documentation with & build guide (PR #149792)

[Ross Brunton via llvm-commits]

================
@@ -6,12 +6,109 @@
 Welcome to Offload's documentation!
 ===================================
 
+Summary
+-------
+
+The Offload subproject aims at providing tooling, runtimes, and APIs that allow
+users to execute code on accelerators or other "co-processors" that may or may
+not match the architecture of their "host". In the long run, all kinds of
+targets are in scope of this effort, including but not limited to: CPUs, GPUs,
+FPGAs, AI/ML accelerators, distributed resources, etc.
+
+For OpenMP offload users, the project is ready and fully usable. The final API
+design is still under development. More content will show up here and on our
+webpage soon. In the meantime, people are encouraged to participate in our
+meetings (see below) and check our `development board
+<https://github.com/orgs/llvm/projects/24/>`_ as well as the discussions on
+`Discourse <https://discourse.llvm.org/tag/offload>`_.
+
 .. toctree::
    :maxdepth: 2
    :caption: Contents:
 
    offload-api
 
+Meetings
+--------
+
+Every second Wednesday, 7:00 - 8:00am PT, starting Jan 24, 2024. Alternates
+with the OpenMP in LLVM meeting. `invite.ics
----------------
RossBrunton wrote:

Did we ever update this invite with the timezone change?

https://github.com/llvm/llvm-project/pull/149792