Fix alignments in github tables

[kdeldycke]

This fix the support of colalign for github table format.

tabulate v0.10 has just been released. It was supposed to fix alignment in markdown tables but it does not.

With the latest master commit I get:

$ uvx -v --from "git+https://github.com/astanin/python-tabulate.git" python -c "from tabulate import tabulate; print(tabulate([['Alice', 24], ['Bob', 19]], headers=['Name', 'Age'], tablefmt='github', colalign=('left', 'right')))"
(...)
DEBUG Attempting GitHub fast path for: git+https://github.com/astanin/python-tabulate.git
DEBUG Attempting to fetch `pyproject.toml` from: https://raw.githubusercontent.com/astanin/python-tabulate/26ccb780f4ae05995485e6f3199bcc5f7214decf/pyproject.toml
DEBUG Solving with target Python version: >=3.14.3
DEBUG Looking at `.dist-info` at: /Users/kde/.cache/uv/archive-v0/8nSHlzFznZ4vHkzGxye7Z/lib/python3.14/site-packages/tabulate-0.10.1.dev34+g26ccb780f.dist-info
(...)
| Name   |   Age |
|--------|-------|
| Alice  |    24 |
| Bob    |    19 |

Instead I am expecting to get:

| Name   |   Age |
|:-------|------:|
| Alice  |    24 |
| Bob    |    19 |

This PR fix this issue, by making github and pipe produce the same syntax.

This PR:

• Closes left, right, and center-aligned Markdown tables #53
• Follow-up on Add support for alignments in Markdown tables #261 (comment)

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.22%. Comparing base (26ccb78) to head (046af03).
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #410      +/-   ##
==========================================
+ Coverage   84.21%   84.22%   +0.01%     
==========================================
  Files           1        1              
  Lines         893      894       +1     
  Branches      217      217              
==========================================
+ Hits          752      753       +1     
  Misses        107      107              
  Partials       34       34              

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[kdeldycke]

Thanks @astanin for the quick merge! :)