notes: Renames and refactors chapter on measures

Author: dead-summer

…is/ch1-measures/1-d-lebesgue-measure.typ …sis/ch1-measure/1-d-lebesgue-measure.typnotes/analysis/ch1-measures/1-d-lebesgue-measure.typ renamed to notes/analysis/ch1-measure/1-d-lebesgue-measure.typ notes/analysis/ch1-measures/1-d-lebesgue-measure.typ renamed to notes/analysis/ch1-measure/1-d-lebesgue-measure.typ

@@ -1,10 +1,10 @@
 #import "../book.typ": *
 
 #show: book-page.with(
-  title: "1 Measures"
+  title: "1 Measure"
 )
 
 
-= Measures
+= Measure
 
 In this chapter we set forth the basic concepts of measure theory, develop a general procedure for constructing nontrivial examples of measures, and apply this procedure to construct measures on the real line.