Add icon for PRQL

[vanillajonathan]

Description

PRQL is a modern language for transforming data — a simple, powerful, pipelined SQL replacement.

https://prql-lang.org/ https://github.com/PRQL/prql

This PR adds a database icon for .prql files.

• Relevant Issues : (none)
• Relevant PRs : (none)
• Type of change :
  • [ ] New feature
  • [ ] Bug fix for existing feature
  • [ ] Code quality improvement
  • [ ] Addition or Improvement of tests
  • [ ] Addition or Improvement of documentation
  • [x] Addition of icon for file extension

[codecov-commenter]

Codecov Report

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

Comparison is base (28c188b) 92.13% compared to head (cc6ef40) 92.13%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #602 +/- ## ======================================= Coverage 92.13% 92.13% ======================================= Files 8 8 Lines 623 623 ======================================= Hits 574 574 Misses 49 49 ```

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