Add least squares flowchart

Author: ivan-pi

README.md

@@ -37,6 +37,23 @@ flowchart TB
 	middle2--No-->b4[HYBRD1]
 ```
 
+Decision tree for nonlinear least squares porblems
+
+```mermaid
+flowchart TB
+	start[Is the Jacobian matrix available?]
+	start--Yes-->m1[Is storage limited?]
+	start--No-->m2[Is flexibility required?]
+	m1--Yes-->ml1[Is flexibility required?]
+	m1--No-->ml2[Is flexibility required?]
+	ml1--Yes-->b1[LMSTR]
+	ml1--No-->b2[LMSTR1]
+	ml2--Yes-->b3[LMDER]
+	ml2--No-->b4[LMDER1]
+	m2--Yes-->mr1[LMDIF]
+	m2--No-->mr2[LMDIF1]
+```
+
 ### Documentation
 
  * The API documentation for the latest default branch can be found [here](https://fortran-lang.github.io/minpack/).  This is generated by processing the source files with [FORD](https://github.com/Fortran-FOSS-Programmers/ford).