docs: bump user-facing semvertag pins to >=0.5.0,<1

Three semvertag>= pins exist in user-facing docs; two were stale:
- README.md:29 quickstart pinned `>=0.1,<1` (pre-0.5.0 baseline)
- docs/providers/github.md:233 "Without the composite action" pure-CLI
  fallback pinned `>=0.3.1,<1` (flagged by PR #16 final review)

Bump both to `>=0.5.0,<1` so every user-facing snippet exposes
--dry-run by default and stays consistent with action.yml's floor.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: lesnik512

README.md

@@ -26,7 +26,7 @@ semvertag:
   before_script:
     - pip install --quiet 'uv>=0.4,<1'
   script:
-    - uvx 'semvertag>=0.1,<1' tag
+    - uvx 'semvertag>=0.5.0,<1' tag
   rules:
     - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
 ```

docs/providers/github.md

@@ -230,7 +230,7 @@ jobs:
         with:
           python-version: "3.13"
       - run: pip install --quiet --no-cache-dir 'uv>=0.4,<1'
-      - run: uvx 'semvertag>=0.3.1,<1' tag
+      - run: uvx 'semvertag>=0.5.0,<1' tag
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 ```