fix and minify images

...ting/bitbucket_importer/bitbucket_import_grant_access.jpg

...ting/bitbucket_importer/bitbucket_import_grant_access.png

...rting/bitbucket_importer/bitbucket_import_new_project.jpg

...rting/bitbucket_importer/bitbucket_import_new_project.png

.../bitbucket_importer/bitbucket_import_select_bitbucket.jpg

.../bitbucket_importer/bitbucket_import_select_bitbucket.png

...ng/bitbucket_importer/bitbucket_import_select_project.png

doc/workflow/importing/import_projects_from_bitbucket.md