Ability to use FASTA files as input

[vkkodali]

From what I can tell, fastp expects the input files to be in FASTQ format. Lately, SRA has stopped including original base qualities in the FASTQ files (all qualities are encoded as ?) which makes read trimming based on quality moot, and makes it pointless to download FASTQ files.

In this context, it would be nice feature to be able to run fastp on FASTA formatted files.