doc(undergrad/overview): add test functions and distributions (#32707)

Author: mcdoll

docs/overview.yaml

@@ -373,7 +373,9 @@ Analysis:
     First Main Theorem of Value Distribution Theory: 'ValueDistribution.characteristic_sub_characteristic_inv_le'
 
   Distribution theory:
+    Test functions: 'TestFunction'
     Schwartz space: 'SchwartzMap'
+    Distributions: 'Distribution'
 
   Fourier analysis:
     Fourier transform as an integral: 'Real.fourier_eq'

docs/undergrad.yaml

@@ -586,13 +586,13 @@ Probability Theory:
 # 12.
 Distribution calculus:
   Spaces $\mathcal{D}(\R^d)$:
-    smooth functions with compact support on $\R^d$: ''
+    smooth functions with compact support on $\R^d$: 'TestFunction'
     stability by derivation: ''
     stability by multiplication by a smooth function: ''
     partitions of unity: ''
     constructing approximations of probability density functions in spaces of common functions (trig, exp, rational, log, etc): ''
   Distributions on $\R^d$:
-    definition of distributions: ''
+    definition of distributions: 'Distribution'
     locally integrable functions as distributions: ''
     derivative of a distribution: ''
     Dirac measures: ''