[libc] finish documenting c23 additions

Such as stdlib.h and tgmath.h

Author: nickdesaulniers

libc/docs/c23.rst

@@ -107,9 +107,59 @@ Additions:
   * unreachable
 * stdlib.h
 
+  * strfromd
+  * strfromf
+  * strfroml
   * free_sized
   * free_aligned_sized
   * memalignment
 * tgmath.h
 
-  * <TODO>
+  * acospi
+  * asinpi
+  * atan2pi
+  * atanpi
+  * compoundn
+  * cospi
+  * erf
+  * exp10m1
+  * exp10
+  * exp2m1
+  * fmaximum
+  * fmaximum_mag
+  * fmaximum_num
+  * fmaximum_mag_num
+  * fminimum
+  * fminimum_mag
+  * fminimum_num
+  * fminimum_mag_num
+  * fromfpx
+  * fromfp
+  * llogb
+  * log10p1
+  * log2p1
+  * logp1
+  * nextdown
+  * nextup
+  * pown
+  * powr
+  * rootn
+  * roundeven
+  * rsqrt
+  * scalbn
+  * sinpi
+  * tanpi
+  * ufromfpx
+  * ufromfp
+  * fadd
+  * dadd
+  * fsub
+  * dsub
+  * fmul
+  * dmul
+  * fdiv
+  * ddiv
+  * ffma
+  * dfma
+  * fsqrt
+  * dsqrt