fix typos in content and contributions

Author: fturmel

content/tracks/side-tracks/pi-day/index.json

@@ -1,6 +1,6 @@
 {
   "title": "Pi Day",
-  "description": "Pi, which is the ratio of a circle's circumference to its diameter, is one of the most important mathematical contants.  This track is a compilation of the many challenges I have completed to calculate Pi.",
+  "description": "Pi, which is the ratio of a circle's circumference to its diameter, is one of the most important mathematical constants. This track is a compilation of the many challenges I have completed to calculate Pi.",
   "videos": [
     "challenges/95-approximating-the-value-of-pi",
     "challenges/96-visualizing-digits-of-pi",

content/tracks/side-tracks/supershapes/index.json

@@ -1,6 +1,6 @@
 {
   "title": "Supershapes!",
-  "description": "This side track is a collection of videos related to supershapes that use spherical coordinates and superformulas.  While not techically a \u201csupershape\u201d, the mandelbulb is constructed in a similar manner and is a SUPER shape.",
+  "description": "This side track is a collection of videos related to supershapes that use spherical coordinates and superformulas. While not technically a \u201csupershape\u201d, the mandelbulb is constructed in a similar manner and is a SUPER shape.",
   "videos": [
     "noc/3-angles/4-polar-coordinates",
     "challenges/19-superellipse",