Add local Playwright testing instructions to CONTRIBUTING.md (#1537)

* Add local Playwright testing instructions to CONTRIBUTING.md

Signed-off-by: James Maa <[email protected]>

* Update CONTRIBUTING.md

Signed-off-by: James Maa <[email protected]>

---------

Signed-off-by: James Maa <[email protected]>

Author: jamesmaa

CONTRIBUTING.md

@@ -30,6 +30,14 @@ Unit tests, integration tests, and various other tests can be executed by runnin
 Other individual tests can be looked up in the [package.json](package.json) file, and the source for specific tests
 can be found in the [test](test) directory
 
+### Playwright
+
+Steps to run [playwright](https://playwright.dev/) tests locally:
+
+1. Run `npx playwright install` to install the headless browsers
+2. Copy the dictionary test data located in the `dictionaries` branch to a directory named `dictionaries` via `git clone --branch dictionaries [email protected]:yomidevs/yomitan.git dictionaries` ([source](https://github.com/yomidevs/yomitan/blob/086e043856ad54cf13cb65f9ba4c63afe8a22cc3/.github/workflows/playwright.yml#L52-L57)).
+3. Now you can run `npx playwright test`. The first run might produce some benign errors complaining about `Error: A snapshot doesn't exist at ...writing actual.`, but subsequent runs should succeed.
+
 ## Building
 
 By default, the development repository is configured for Chrome, and the [ext](ext) directory can be directly