chore: document known failures (#646)

.github/workflows/motoko-defi-example.yml

@@ -1,3 +1,4 @@
+# known failure: https://dfinity.atlassian.net/browse/EM-1
 name: motoko-defi
 on:
   push:

.github/workflows/motoko-ledger-transfer-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-5
 name: motoko-ledger-transfer
 on:
   push:

.github/workflows/rust-basic-dao-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-4
 name: rust-basic-dao
 on:
   push:

.github/workflows/rust-defi-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-2
 name: rust-defi
 on:
   push:

.github/workflows/rust-encrypted-notes-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-3
 name: rust-encrypted-notes
 on:
   push:

.github/workflows/rust-pub-sub-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-6
 name: rust-pub-sub
 on:
   push:

.github/workflows/rust-threshold-ecdsa-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-7
 name: rust-threshold-ecdsa
 on:
   push:

.github/workflows/rust-tokens-transfer-example.yml

@@ -1,3 +1,4 @@
+# Known failure: https://dfinity.atlassian.net/browse/EM-5
 name: rust-tokens_transfer
 on:
   push: