More documentation for setting spider atributes

* docs: require sphinx-rtd-theme>=0.5.2 and the latest pip to prevent installing breaking docutils>=0.17

* Update feed-exports.rst

* Update feed-exports.rst

* Reflects the comments

* Remove redundant newline

* Update docs/topics/feed-exports.rst

Co-authored-by: Adrián Chaves <adrian@chaves.io>

* Apply suggestions from code review

Co-authored-by: Adrián Chaves <adrian@chaves.io>

Co-authored-by: Adrián Chaves <adrian@chaves.io>
Co-authored-by: Eugenio Lacuesta <eugenio.lacuesta@gmail.com>

docs/topics/feed-exports.rst

@@ -135,6 +135,9 @@ Here are some examples to illustrate:
 
     -   ``s3://mybucket/scraping/feeds/%(name)s/%(time)s.json``
 
+.. note:: :ref:`Spider arguments <spiderargs>` become spider attributes, hence 
+          they can also be used as storage URI parameters.
+
 
 .. _topics-feed-storage-backends:
 

docs/topics/spiders.rst

@@ -294,6 +294,14 @@ The above example can also be written as follows::
         def start_requests(self):
             yield scrapy.Request(f'http://www.example.com/categories/{self.category}')
 
+If you are :ref:`running Scrapy from a script <run-from-script>`, you can 
+specify spider arguments when calling 
+:class:`CrawlerProcess.crawl <scrapy.crawler.CrawlerProcess.crawl>` or
+:class:`CrawlerRunner.crawl <scrapy.crawler.CrawlerRunner.crawl>`::
+
+    process = CrawlerProcess()
+    process.crawl(MySpider, category="electronics")
+
 Keep in mind that spider arguments are only strings.
 The spider will not do any parsing on its own.
 If you were to set the ``start_urls`` attribute from the command line,