Allows drawing recursive relationships

[syou6162]

resolves https://github.com/datnguye/dbterd/issues/88

Description

This modification allows a diagram to be drawn even if it has the following recursive relationship.

erDiagram
  "MY_PROJECT.CATEGORY" {
  }
  "MY_PROJECT.CATEGORY" }|--|| "MY_PROJECT.CATEGORY": categoryid--parentCategoryId

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have run this code in development and it appears to resolve the stated issue
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [x] I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR

[codecov[bot]]

Codecov Report

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

Comparison is base (f704cf8) 100.00% compared to head (681134f) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #89 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 32 32 Lines 959 961 +2 ========================================= + Hits 959 961 +2 ```

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[datnguye]

LGTM thanks @syou6162