Adds tip regarding automatic single query filter generation to docs

[fireteam99]

Description

Updates documentation regarding automatic single query primary key filter generation.

Types of Changes

• [ ] Core
• [ ] Bugfix
• [ ] New feature
• [ ] Enhancement/optimization
• [x] Documentation

Issues Fixed or Closed by This PR

• https://github.com/strawberry-graphql/strawberry-graphql-django/issues/329

Checklist

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (981fb93) 87.90% compared to head (0d72d0a) 87.90%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #341 +/- ## ======================================= Coverage 87.90% 87.90% ======================================= Files 33 33 Lines 2944 2944 ======================================= Hits 2588 2588 Misses 356 356 ```

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