Script to create a Changelog.md entry from files in .changelog

[j-rivero]

Still a work in progress. Part of #246.

The script consumes entries in the a .changelog/ directory and generates a Changelog.md modification. It can not bump the version yet.

In a test run on the gz-test repository. This is the initial files:

gz-test on  jrivero/changelogs [!] via △ v3.28.3 ❯ ls .changelog/
fix-bug-entry.md
new-feature.md
update-license.md  (comming from PR2)

The run founds the commits and the PRs that belongs to the commits in any:

gz-test on  jrivero/changelogs [!] via △ v3.28.3 ❯ ./create_changelog_entry.py 
Reading changelog entries from /home/jrivero/code/gz/gz-test/.changelog...
Found commit SHA: 26b1ab64abf66d57164d8bdb10a8e851827c88f1 for file update-license.md
Found PR #2 for commit 26b1ab64abf66d57164d8bdb10a8e851827c88f1
Found commit SHA: 30ad3e8ba311fc827cef3827a9cb5d6d976b2b96 for file fix-bug-entry.md
Found commit SHA: 30ad3e8ba311fc827cef3827a9cb5d6d976b2b96 for file new-feature.md
Generating changelog entry...
Generated changelog entry:
--------------------------------------------------
## Gazebo Test 0.x.x (2025-06-16)

* Update license years from 2012 to 2025
    * [Pull request #2](https://github.com/gazebosim/gz-test/pull/2)
* Fix issue #468
    * [Commit #30ad3e8ba311fc827cef3827a9cb5d6d976b2b96](30ad3e8ba311fc827cef3827a9cb5d6d976b2b96)
* Oneway service request from the command line
    * [Commit #30ad3e8ba311fc827cef3827a9cb5d6d976b2b96](30ad3e8ba311fc827cef3827a9cb5d6d976b2b96)

--------------------------------------------------
Update Changelog.md with this entry? (y/N): y
Successfully updated /home/jrivero/code/gz/gz-test/Changelog.md
Remove processed changelog entry files? (y/N): y

The deleted files and the modified changelog:

gz-test on  jrivero/changelogs [✘!] via △ v3.28.3 ❯ git status
On branch jrivero/changelogs
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        deleted:    .changelog/fix-bug-entry.md
        deleted:    .changelog/new-feature.md
        deleted:    .changelog/update-license.md

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   Changelog.md

And the generated changelog diff:

gz-test on  jrivero/changelogs [✘!] via △ v3.28.3 ❯ git diff Changelog.md
diff --git a/Changelog.md b/Changelog.md
index f602ed1..63b3b8e 100755
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,4 +1,14 @@
 ## Gazebo Test 0.x
 
+## Gazebo Test 0.x.x (2025-06-16)
+
+* Update license years from 2012 to 2025
+    * [Pull request #2](https://github.com/gazebosim/gz-test/pull/2)
+* Fix issue #468
+    * [Commit #30ad3e8ba311fc827cef3827a9cb5d6d976b2b96](30ad3e8ba311fc827cef3827a9cb5d6d976b2b96)
+* Oneway service request from the command line
+    * [Commit #30ad3e8ba311fc827cef3827a9cb5d6d976b2b96](30ad3e8ba311fc827cef3827a9cb5d6d976b2b96)
+
+
 ## Gazebo Test 0.x.x (2022-xx-xx)
 
gz-test on  jrivero/changelogs [✘!] via △ v3.28.3 ❯ 

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