Update line on methods, update TS definition to allow strings (#3802)

Fixes #3140

Co-authored-by: Jay <jasonsaayman@gmail.com>

README.md

@@ -231,7 +231,7 @@ axios('/user/12345');
 
 ### Request method aliases
 
-For convenience aliases have been provided for all supported request methods.
+For convenience, aliases have been provided for all common request methods.
 
 ##### axios.request(config)
 ##### axios.get(url[, config])

index.d.ts

@@ -74,7 +74,7 @@ export interface TransitionalOptions {
 
 export interface AxiosRequestConfig<D = any> {
   url?: string;
-  method?: Method;
+  method?: Method | string;
   baseURL?: string;
   transformRequest?: AxiosRequestTransformer | AxiosRequestTransformer[];
   transformResponse?: AxiosResponseTransformer | AxiosResponseTransformer[];