.gitignore: Ignore top-level entries only

Update .gitignore to ignore only top-level entries by prefixing them
with `/`.
Also ignore KraftKit-generated configuration files (names starting with
`.config.`)

Signed-off-by: Razvan Deaconescu <[email protected]>
Reviewed-by: Stefan Jumarea <[email protected]>
Approved-by: Stefan Jumarea <[email protected]>
GitHub-Closes: #27

Author: razvand

.gitignore

@@ -1,4 +1,5 @@
-build/
-.config
-.unikraft/
+/build/
+/.config
+/.config.*
+/.unikraft/
 /workdir/