fix: adding docstrings to the files where it was missing (#2101)

* fix: adding docstrings to missing files

* style: format code

* style: improve formatting

Co-authored-by: Jagruti Tiwari <jagrutit@cdac.in>
Co-authored-by: rickstaa <rick.staa@outlook.com>

src/calculateRank.js

@@ -1,4 +1,14 @@
-// https://stackoverflow.com/a/5263759/10629172
+/**
+ * Calculates the probability of x taking on x or a value less than x in a normal distribution
+ * with mean and standard deviation.
+ *
+ * @see https://stackoverflow.com/a/5263759/10629172
+ *
+ * @param {string} mean
+ * @param {number} sigma
+ * @param {number} to
+ * @returns {number} Probability.
+ */
 function normalcdf(mean, sigma, to) {
   var z = (to - mean) / Math.sqrt(2 * sigma * sigma);
   var t = 1 / (1 + 0.3275911 * Math.abs(z));
@@ -16,6 +26,18 @@ function normalcdf(mean, sigma, to) {
   return (1 / 2) * (1 + sign * erf);
 }
 
+/**
+ * Calculates the users rank.
+ *
+ * @param {number} totalRepos
+ * @param {number} totalCommits
+ * @param {number} contributions
+ * @param {number} followers
+ * @param {number} prs
+ * @param {number} issues
+ * @param {number} stargazers
+ * @returns {{level: string, score: number}}} The users rank.
+ */
 function calculateRank({
   totalRepos,
   totalCommits,