.gitignore: Update .gitignore for doc temp file.

Signed-off-by: zhanglinjing <Linjing.Zhang@infineon.com>

Author: LinjingZhang

.gitignore

@@ -10,6 +10,7 @@ build
 # python
 **/__pycache__/
 venv/
+myenv/
 
 # code-check standards and reports
 misra.txt
@@ -20,3 +21,9 @@ scan-build-reports/
 cppcheck_reports/
 cppcheck.checkers
 err.xml
+
+# Ignore docs build (Sphinx)
+docs/build
+docs/source/_build
+__pycache__/
+_build/