Add line for PyCharm IDE in gitignore file

There was no entry in the gitignore file for JetBrains IDEs like PyCharm.
This patch adds an entry to ignore the .idea directory that is created
when the manila-tempest-plugin git tree is imported as a project into
PyCharm.

Change-Id: I1e185976f9d1467eefe96548a2e090d1dd30ffca
1 file changed