Minor proofreading changes to JOSS paper.

Garner's Modern English Usage (4th ed.) recommends "webpage" over "web page."

paper/paper.md

@@ -41,13 +41,13 @@ to the ``<canvas>`` drawing surface used by the viewer.
 
 An application programming interface (API) is provided, which allows external
 code to control the viewer and implement features such as custom buttons or
-integration with other web page elements. One such example is integrating the
+integration with other webpage elements. One such example is integrating the
 viewer with a map [@Gede2015; @Albrizio2013; @OSM2018]; the locations where
 panoramas were taken can be displayed as markers on the map, whereby clicking a
 marker will open the corresponding panorama in the viewer. Panoramic
 videos---videos that cover up to a full 360 degrees of azimuth---are supported
 via a bundled extension, which is built using
-the API. The underlying rendering code is separate from the user interface
+the API. The viewer's underlying rendering code is separate from the user interface
 code, which allows for more extensive customization and tighter integration
 with external code, if desired. This rendering code uses a pinhole camera model
 for equirectangular panoramas implemented as a WebGL fragment shader, instead
@@ -61,7 +61,7 @@ applications range from cartography [@Gede2015] to digital humanities
 education [@Herault2018]. It has also found use in public outreach
 applications, such as its use by the European Southern Observatory to display
 panoramas of their observatories [@ESO2017]. _Pannellum_ is intended to be used
-any time an interactive panorama needs to be displayed in a web page, be it an
+any time an interactive panorama needs to be displayed on a webpage, be it an
 internal research application or a publicly accessible website. It may also
 work with certain mobile application frameworks, but such use is not officially
 supported. [Documentation](https://pannellum.org/documentation/overview/) and