Merge branch 'feature/alt_text' into 'master'

add alt text for images

See merge request !39

docs/architecture.md

@@ -37,7 +37,7 @@ microsoft) and other services use OIDC.
 X.509 user-certificates may also be used at different places, but there is
 a general trend to deprecate them (for user authentication).
 
-![NFDI AAI Architecture v2.5](images/nfdi-aai-options-v2.5-glow.png){: style="width:700px"}
+![Hierarchical view of the NFDI architecture diagram that follows the AARC Blueprint Architecture. eduGAIN and other IdPs are in the identity layer on top, followed by the Edu-ID proxy and then by the Community AAI proxies. The Community AAI proxies can connect to community services. The bottom layer shows the NFDI infrastructure proxy which connects to multiple Community AAI proxies and targets NFDI infrastructure services which are relevant for multiple communities.  ](images/nfdi-aai-options-v2.5-glow.png "NFDI AAI Architecture v2.5"){: style="width:700px"}
 
 !!! info
 

docs/policies.md

@@ -4,7 +4,7 @@
 
 Our policy table gives an overview who needs to read or write which policy
 
-[![policy_table](https://codebase.helmholtz.cloud/m-team/nfdi/nfdi-policies/-/jobs/artifacts/v0.9.3/raw/images/tabelle_policy-framework.png?job=build-docs){: style="height:280px"}](https://codebase.helmholtz.cloud/m-team/nfdi/nfdi-policies/-/jobs/artifacts/v0.9.3/raw/images/tabelle_policy-framework.png?job=build-docs)
+[![Matrix which explains which entities define (rows) and comply to (columns) the different policy documents introduced on this page. Refer to the individual documents for details.](https://codebase.helmholtz.cloud/m-team/nfdi/nfdi-policies/-/jobs/artifacts/v0.9.3/raw/images/tabelle_policy-framework.png?job=build-docs "policy_table"){: style="height:280px"}](https://codebase.helmholtz.cloud/m-team/nfdi/nfdi-policies/-/jobs/artifacts/v0.9.3/raw/images/tabelle_policy-framework.png?job=build-docs)
 
 
 ## NFDI Policies