Updates integrity verification docs in Core (#609)

* Adds an action to validate proposed PRs

Signed-off-by: Alexios Zavras (zvr) <github@zvr.gr>

* Adds info about other possible verification methods.

Signed-off-by: Alexios Zavras (zvr) <github@zvr.gr>

* Replaces the wrongly added workflow with the current one

Signed-off-by: Alexios Zavras (zvr) <github@zvr.gr>

---------

Signed-off-by: Alexios Zavras (zvr) <github@zvr.gr>
Co-authored-by: Gary O'Neall <gary@sourceauditor.com>

model/Core/Classes/Hash.md

@@ -13,8 +13,11 @@ of applying a mathematical algorithm
 that maps data of arbitrary size to a bit string (the hash)
 and is a one-way function, that is,
 a function which is practically infeasible to invert.
+
 This is commonly used for integrity checking of data.
 
+Please note that different profiles may also provide additional methods for verifying the integrity of specific subclasses of Elements.
+
 ## Metadata
 
 - name: Hash

model/Core/Classes/IntegrityMethod.md

@@ -13,6 +13,8 @@ of a specific Element that correlates to the data in this SPDX document. This id
 a recipient to determine if anything in the original Element has been changed and eliminates
 confusion over which version or modification of a specific Element is referenced.
 
+Please note that different profiles may also provide additional methods for verifying the integrity of specific subclasses of Elements.
+
 ## Metadata
 
 - name: IntegrityMethod

model/Core/Properties/verifiedUsing.md

@@ -10,6 +10,8 @@ Provides an IntegrityMethod with which the integrity of an Element can be assert
 
 VerifiedUsing provides an IntegrityMethod with which the integrity of an Element can be asserted.
 
+Please note that different profiles may also provide additional methods for verifying the integrity of specific subclasses of Elements.
+
 ## Metadata
 
 - name: verifiedUsing