Docs : Removed typos and grammatical errors.

Author: shivanshu1234

docs/contribute.rst

@@ -47,7 +47,7 @@ We have a strict code style that is easy to follow since you just have to
 install `pre-commit`_ and it will automatically run different linting tools
 (`autoflake`_, `autopep8`_, `docformatter`_, `isort`_, `prospector`_, `unify`_
 and `yapf`_) to check your changes before you commit them. `pre-commit` will let
-you know if there were any problems that is wasn't able to fix automatically.
+you know if there were any problems that it wasn't able to fix automatically.
 
 To run the `pre-commit` command and check your changes:
 

docs/install.rst

@@ -127,9 +127,9 @@ you can use the admin interface via http://127.0.0.1:8000/admin
 (logging in with the superuser account you just created).
 
 For builds to properly work as expected,
-it is necessary the port you're serving on
+it is necessary that the port you're serving on
 (i.e. ``python manage.py runserver 0.0.0.0:8080``)
-match the port defined in ``PRODUCTION_DOMAIN``.
+matches the port defined in ``PRODUCTION_DOMAIN``.
 You can use ``readthedocs/settings/local_settings.py`` to modify this
 (by default, it's ``localhost:8000``).
 
@@ -141,8 +141,8 @@ For example to update the ``pip`` repo::
 
 .. note::
 
-    If you have problems building successfully a project,
-    probably is because some missing libraries for ``pdf`` and ``epub`` generation.
+    If you have problems building a project successfully,
+    it is probably because of some missing libraries for ``pdf`` and ``epub`` generation.
     You can uncheck this on the advanced settings of your project.
 
 What's available