chore: add new team member astiwana (#34373)

### Issue # (if applicable)

N/A

### Reason for this change

Adding new team member's GitHub account

### Description of changes

Added my GitHub username

### Describe any new or updated permissions being added

N/A


### Description of how you validated changes

N/A

### Checklist
- [ ] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: astiwana

.github/workflows/github-merit-badger.yml

@@ -17,4 +17,4 @@ jobs:
           badges: '[beginning-contributor,repeat-contributor,valued-contributor,admired-contributor,star-contributor,distinguished-contributor]'
           thresholds: '[0,3,6,13,25,50]'
           badge-type: 'achievement'
-          ignore-usernames: '[rix0rrr,iliapolo,otaviomacedo,kaizencc,TheRealAmazonKendra,mrgrain,pahud,kellertk,ashishdhingra,khushail,moelasmar,paulhcsun,GavinZZ,xazhao,gracelu0,shikha372,godwingrs22,bergjaak,IanKonlog,Leo10Gama,samson-keung,scorbiere,jiayiwang7,saiyush,5d,iankhou,QuantumNeuralCoder,SimonCMoore,Y-JayKim,ykethan,aws-cdk-automation,dependabot[bot],mergify[bot],aemada-aws]'
+          ignore-usernames: '[rix0rrr,iliapolo,otaviomacedo,kaizencc,TheRealAmazonKendra,mrgrain,pahud,kellertk,ashishdhingra,khushail,moelasmar,paulhcsun,GavinZZ,xazhao,gracelu0,shikha372,godwingrs22,bergjaak,IanKonlog,Leo10Gama,samson-keung,scorbiere,jiayiwang7,saiyush,5d,iankhou,QuantumNeuralCoder,SimonCMoore,Y-JayKim,ykethan,astiwana,aws-cdk-automation,dependabot[bot],mergify[bot],aemada-aws]'

.mergify.yml

@@ -65,7 +65,7 @@ pull_request_rules:
       label:
         add: [contribution/core]
     conditions:
-      - author~=^(rix0rrr|iliapolo|otaviomacedo|kaizencc|TheRealAmazonKendra|mrgrain|pahud|ashishdhingra|kellertk|moelasmar|paulhcsun|GavinZZ|xazhao|gracelu0|shikha372|QuantumNeuralCoder|godwingrs22|bergjaak|samson-keung|IanKonlog|Leo10Gama|scorbiere|jiayiwang7|saiyush|5d|iankhou|SimonCMoore|Y-JayKim|ykethan|aemada-aws)$
+      - author~=^(rix0rrr|iliapolo|otaviomacedo|kaizencc|TheRealAmazonKendra|mrgrain|pahud|ashishdhingra|kellertk|moelasmar|paulhcsun|GavinZZ|xazhao|gracelu0|shikha372|QuantumNeuralCoder|godwingrs22|bergjaak|samson-keung|IanKonlog|Leo10Gama|scorbiere|jiayiwang7|saiyush|5d|iankhou|SimonCMoore|Y-JayKim|ykethan|astiwana|aemada-aws)$
       - -label~="contribution/core"
   - name: automatic merge
     actions: