Adds Intellij IDEA files to .gitignore (#3389)

### Motivation and Context

Intellij IDEA is heavy used in the Java ecosystem, so it would be good
to have default files in the .gitignore

### Description

Add the default Intellij IDEA working files and directory to the
.gitignore

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Co-authored-by: Bruno Borges <brborges@microsoft.com>
Co-authored-by: David Grieve <dsgrieve@yahoo.com>

.gitignore

@@ -409,14 +409,19 @@ FodyWeavers.xsd
 *.key
 *.pem
 
+# JetBrains IntelliJ
+.idea
+*.ipr
+*.iml
+*.iws
+
 .env
 certs/
 launchSettings.json
 config.development.yaml
 *.development.config
 *.development.json
 .DS_Store
-.idea/
 node_modules/
 obj/
 bin/