Fix some spelling errors.

.codespell-ignore

@@ -0,0 +1,8 @@
+# codespell dictionary entries
+Fram
+dropse
+figurestyle
+fram
+hist
+namd
+rouge

Makefile

@@ -154,7 +154,7 @@ lesson-fixme :
 
 ## spellcheck
 spellcheck:
-	codespell --skip="assets,*.svg,.vendor" --quiet-level=2  -L "dropse,figurestyle,fram,hist,namd,rouge"
+	codespell --skip="assets,*.svg,.vendor" --quiet-level=2  -I .codespell-ignore
 
 ##
 ## IV. Auxililary (plumbing) commands

_extras/discuss.md

@@ -82,7 +82,7 @@ individual to individual!
 >
 > - Vary the number of threads used per process
 > - Reduce the number of cores used per node
-> - Allow the calculation to use Symmetric Mutithreading (SMT) if enabled
+> - Allow the calculation to use Symmetric Multithreading (SMT) if enabled
 >
 > Please ask for more information on these options from a helper!
 {: .challenge}
@@ -95,7 +95,7 @@ https://blast.ncbi.nlm.nih.gov/Blast.cgi?CMD=Web&PAGE_TYPE=BlastDocs&DOC_TYPE=Do
 > compares nucleotide or protein sequences to sequence databases and calculates
 > the statistical significance.
 >
-> In this exercise, you should use what you have learnt so far to set up a way
+> In this exercise, you should use what you have learned so far to set up a way
 > to run multiple serial BLAST+ analyses in parallel. There are many different
 > ways to do this that can be used on their own or in combination. Some ideas
 > include: