build: added Gemini Code Assistant for GitHub (#854)

Author: kikoso

.gemini/config.yaml

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+# Gemini Code Assist Configuration
+# See: https://developers.google.com/gemini-code-assist/docs/customize-gemini-behavior-github
+
+# Feature settings
+have_fun: false
+
+code_review:
+  disable: false
+  comment_severity_threshold: MEDIUM
+  max_review_comments: -1
+
+pull_request_opened:
+  summary: true
+  code_review: true
+  include_drafts: true
+
+# Files to ignore in Gemini analysis
+ignore_patterns:
+  - "**/*.bin"
+  - "**/*.exe"
+  - "**/build/**"
+  - "**/.gradle/**"
+  - "**/secrets.properties"

.gemini/styleguide.md

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+# Gemini Code Assist Style Guide: android-maps-compose
+
+This guide defines the custom code review and generation rules for the `android-maps-compose` project.
+
+## Jetpack Compose Guidelines
+- **API Guidelines**: Strictly follow the [Jetpack Compose API guidelines](https://github.com/androidx/androidx/blob/androidx-main/compose/docs/compose-api-guidelines.md).
+- **Naming**: Composable functions must be PascalCase.
+- **State Management**: Prefer library-provided state holders like `rememberCameraPositionState` or `MarkerState`.
+- **Modifiers**: The first optional parameter of any Composable should be `modifier: Modifier = Modifier`.
+
+## Kotlin Style
+- **Naming**: Use camelCase for variables and functions.
+- **Documentation**: Provide KDoc for all public classes, properties, and functions.
+- **Safety**: Use null-safe operators and avoid `!!`.
+
+## Project Specifics
+- **Secrets**: Never commit API keys. Ensure they are read from `secrets.properties` via `BuildConfig` or similar.
+- **Maps SDK**: Use the components provided in `maps-compose`, `maps-compose-utils`, and `maps-compose-widgets` rather than raw `GoogleMap` objects.