feat: add preset event _page_load

[zhu-xiaowei]

Description

1. add preset event _page_load

General Checklist

• [x] Added new tests to cover change, if needed
• [ ] Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• [x] Documentation update for the change if required
• [x] PR title conforms to conventional commit style
• [ ] If breaking change, documentation/changelog update with migration instructions

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (95ea1ec) 100.00% compared to head (2ed4083) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #40 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 24 25 +1 Lines 1038 1073 +35 Branches 193 202 +9 ========================================= + Hits 1038 1073 +35 ```

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