add "Team Roles" section to "Issue Triage" page

Author: lolbinarycat

src/release/issue-triaging.md

@@ -80,7 +80,7 @@ Note that some labels may only be applied by users with write access to [`rust-l
 There are many different labels that can be applied to issues.
 
 - `needs-triage`: Signals that an issue is new and needs initial triage.
-- [`T-*`]: Specifies the team or teams that this issue is relevant to. For example `T-compiler`, `T-types` or `T-libs`.
+- [`T-*`]: Specifies the team or teams that this issue is relevant to. For example `T-compiler`, `T-types` or `T-libs`.  See [Team Roles](#team-roles) for more details.
 - [`WG-*`]: Specifies the working groups that this issue is relevant to, for example `WG-debugging`.
 - [`PG-*`]: Specifies the project groups that this issue is relevant to, for example the `PG-exploit-mitigations`.
 - [`C-*`]: Specifies the category of the label, for example a bug, tracking issue or discussion.
@@ -145,6 +145,26 @@ There are many different labels that can be applied to issues.
   - An FCP will also cause a relnotes issue to be created, if it's started on an issue.
 - [`metabug`]: Tracks other bugs.
 
+#### Team roles
+
+Most of the teams have fairly obvious roles,
+like `T-compiler` handling everything related to the compiler,
+but some teams are less self-explantory.
+
+* `T-libs` handles the *implementation* of the standard libraries,
+  as well as presentation and organization details of library docs, such as spelling and structure.
+* `T-libs-api` handles the *semantics* of standard libraries,
+  such as type signatures, the addition of new functions,
+  and what gurantees are and are not made by the documentation of functions
+  (this includes error handling and platform-specific behavior).
+* `T-lang` handles the semantics of language features themselves, such as keywords.
+  This includes the keyword docs in the standard library.
+* `T-spec` maintains [the reference](https://github.com/rust-lang/reference/).
+* `T-opsem` handles the operational semantics of the abstract machine,
+  which defines what unsafe code is allowed to do without causing Undefined Behavior.
+  This is covered in [the nomicon](https://doc.rust-lang.org/nomicon/),
+  as well as some parts of library docs, such as in `core::ptr`.
+
 ### Creating labels
 
 <div class="warning">