Add @Bromeon and @EmbersArc as CODEOWNERS for egui_plot (#3711)

Please take a look @Bromeon and @EmbersArc!

You have both contributed substantially to `egui_plot` (more than I
have).
This is me inviting you to co-maintain the `egui_plot` crate.
If you accept, you'll get a notification when someone opens a PR
touching `egui_plot`, and you can review and merge it as you see fit.
You can also merge your own egui_plot PRs without waiting on me to
review them.

CODEOWNERS

@@ -0,0 +1 @@
+/crates/egui_plot @Bromeon @EmbersArc

crates/egui_plot/Cargo.toml

@@ -1,7 +1,11 @@
 [package]
 name = "egui_plot"
 version.workspace = true
-authors = ["Emil Ernerfeldt <[email protected]>"]
+authors = [
+    "Emil Ernerfeldt <[email protected]>",    # https://github.com/emilk
+    "Jan Haller <[email protected]>",                 # https://github.com/Bromeon
+    "Sven Niederberger <[email protected]>", # https://github.com/EmbersArc
+]
 description = "Immediate mode plotting for the egui GUI library"
 edition.workspace = true
 rust-version.workspace = true