Improve generic extension in search and getSearch

[cvermand]

In the following methods:

meilisearch-js/src/indexes.ts

Line 102 in b1ed904

 async searchGet<D = T>( 

and

meilisearch-js/src/indexes.ts

Line 79 in b1ed904

 async search<D = T>( 

The generic D should always extend Record<string, any>.

Thus, they should be added in the generic definition like this

 async searchGet<D extends Record<string, any> = T>