ci: Update release-plz to make use of backport links for the changelog

.release-plz.toml

@@ -1,3 +1,48 @@
 [workspace]
 git_release_name = "{{ version }}"
 git_tag_name = "{{ version }}"
+
+[changelog]
+body = """
+## [{{ version | trim_start_matches(pat="v") }}]\
+    {%- if release_link -%}\
+        ({{ release_link }})\
+    {% endif %} \
+    - {{ timestamp | date(format="%Y-%m-%d") }}
+{% for group, commits in commits | group_by(attribute="group") %}
+### {{ group | upper_first }}
+    {% for commit in commits %}
+        - {% if commit.scope -%}{{ commit.scope | upper_first }}: {% endif %}
+        {%- if commit.breaking %}[**breaking**] {% endif %}
+        {{- commit.message }}
+        {%- if commit.links %} ([{{ commit.links.1.text }}]({{ commit.links.1.href }})){% endif -%}
+    {% endfor %}
+{% endfor %}
+{%- if github -%}
+{% if github.contributors | filter(attribute="is_first_time", value=true) | length != 0 %}
+  ## New Contributors ❤️
+{% endif %}\
+{% for contributor in github.contributors | filter(attribute="is_first_time", value=true) %}
+  * @{{ contributor.username }} made their first contribution
+    {%- if contributor.pr_number %} in \
+      [#{{ contributor.pr_number }}]({{ self::remote_url() }}/pull/{{ contributor.pr_number }}) \
+    {%- endif %}
+{%- endfor -%}
+{%- endif %}
+"""
+
+commit_parsers = [
+  { message = '(?i)^(\w+: )?feat', group = "added" },
+  { message = '(?i)^(\w+: )?add', group = "added" },
+  { message = '(?i)^(\w+: )?change', group = "changed" },
+  { message = '(?i)^(\w+: )?deprecate', group = "deprecated" },
+  { message = '(?i)^(\w+: )?remove', group = "removed" },
+  { message = '(?i)^(\w+: )?fix', group = "fixed" },
+  { message = '(?i)^(\w+: )?fix', group = "fixed" },
+  { message = '^.*', group = "other" },
+]
+
+link_parsers = [
+    # Extract backport patterns
+    { pattern = '\(backport <.*/(\d+)>\)', text = "#$1", href = "https://github.com/rust-lang/libc/pulls/$1"}
+]