Write introduction to the annotation pipeline

Author: marinak-ebi

annotation_pipeline/README.md

@@ -1,3 +1,10 @@
+# IMPC Annotation Pipeline
+The IMPC annotation pipeline assigns Mammalian Phenotype (MP) terms to significant genetic effects based on a p-value threshold of 0.0001. The goal is to associate phenotypic observations with the corresponding genetic modifications.
+At the IMPC, genetic effects are identified using three statistical analysis platforms:
+1. Linear Mixed Model framework or MM
+2. Fisher Exact Test framework or FE
+3. Reference Range Plus Test framework or RR
+
 ```mermaid
 %%{
     init: {