Add content for numbers-to-indices/overview

Add actual content to the skeleton of the `numbers-to-indices/overview`
section.

Signed-off-by: Eggert Karl Hafsteinsson <[email protected]>
Signed-off-by: Teodor Dutu <[email protected]>
Signed-off-by: Razvan Deaconescu <[email protected]>

chapters/numbers-to-indices/overview/reading/README.md

@@ -1,10 +1,10 @@
 # Numbers to Indices In R
 
-1. [Numbers, Arithmetic and Basic Algebra](./numbers-arithmetic-basic-algebra.md)
-1. [Data Vectors](./data-vectors.md)
-1. [More on Algebra](./more-algebra.md)
-1. [Discrete Random Variables and the Binomial Distribution](discrete-random-vars-binomial-distribution.md)
-1. [Functions](./functions.md)
-1. [Polynomials](./polynomials.md)
-1. [Simple Data Analysis in R](./simple-data-analysis-r.md)
-1. [Indices and the apply Commands in R](./indices-apply-commands-r.md)
+1. [Numbers, Arithmetic and Basic Algebra](../../numbers-arithmetic-basic-algebra/reading/README.md)
+1. [Data Vectors](../../data-vectors/reading/README.md)
+1. [More on Algebra](../../more-algebra/reading/README.md)
+1. [Discrete Random Variables and the Binomial Distribution](../../discrete-random-vars-binomial-distribution/reading/README.md)
+1. [Functions](../../functions/reading/README.md)
+1. [Polynomials](../../polynomials/reading/README.md)
+1. [Simple Data Analysis in R](../../simple-data-analysis-r/reading/README.md)
+1. [Indices and the apply Commands in R](../../indices-apply-commands-r/reading/README.md)