Update git, docker ignore files

- Remove unnecessary rule for .rs.bk, rustfmt has been defaulting to
  overwrite for a very long time now
- Move server/svix-server/.gitignore rules up to server/.gitignore
- Import missing ignores to .dockerignore

server/.dockerignore

@@ -1,12 +1,19 @@
-# will have compiled files and executables
-target/
+## From .gitignore
+# Cargo's artifact dir
+/target/
 
-/tmp
+# Server config files
+/svix-server/config.toml
+.env
 
-# These are backup files generated by rustfmt
-**/*.rs.bk
+# IDE
+Session.vim
 
-# MSVC Windows builds of rustc generate these, which store debugging information
+# MSVC debug files
 *.pdb
 
+# Sometimes convenient to have a tempdir for files not tracked by git
+tmp/
+
+## Docker-specific ignores
 Dockerfile

server/.gitignore

@@ -1,16 +1,15 @@
-# Generated by Cargo
-# will have compiled files and executables
-debug/
-target/
+# Cargo's artifact dir
+/target/
 
-/tmp
+# Server config files
+/svix-server/config.toml
+.env
 
-# These are backup files generated by rustfmt
-**/*.rs.bk
+# IDE
+Session.vim
 
-# MSVC Windows builds of rustc generate these, which store debugging information
+# MSVC debug files
 *.pdb
 
-Session.vim
-
-.env
+# Sometimes convenient to have a tempdir for files not tracked by git
+tmp/